THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 


PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


NORTHWESTERN  U#TVERS!TY 
MEDICAL  SCHOOL  LIBRARY. 

A     MANUAL 


HISTOLOGY 


EDITED   AND  PREPARED  BY 

THOMAS  E.  SATTERTHWAITE,  M.D., 


OF  NEW  YOKK 


President  of  the  New  York  Pathological  Society,  Pathologist  to  the  St.  Luke's  and 
Presbyterian  Hospitals,  etc. 


IN    ASSOCIATION   WITH 

DRS.   THOMAS   D WIGHT,  J.  COLLINS  WARREN,  WILLIAM  F.  WHITNEY,  CLARENCE  J. 
BLAKE,  and  C.  H.  WILLIAMS,  of  Boston;  DR.  J.  HENRY  C.  SIMES,  of  Philadel- 
phia ;  Dit.  BENJAMIN  F.  WESTBROOK,  of  Brooklyn ;  and  DHS.  EDMUND  C. 
WENDT,  ABRAHAM  MAYER,  R.  W.  AMIDON,  A.  R.  ROBINSON,  W.  R. 
BIRDSALL,  D.  BRYSON  DELAY  AN,  C.  L.  DANA,  and  W.  H. 
PORTER,    of   New  York   City 


WITH   ONE  HUNDRED   AND    NINETY-EIGHT  ILLUSTRATIONS 


NEW   YOKK 
WILLIAM    WOOD    &    COMPANY 

1881 


COPYRIGHT  BY 

WILLIAM  WOOD  &  COMPANY 
1881 


TROW'S 

PRINTING  AND  BOOKBINDING  COMPANY 

201-213  East  iztk  Street 

NEW  YORK 


PREFACE. 


FOR  some  years  past  there  has  been  a  general  demand 
among  the  members  of  our  profession  for  a  manual  of  Histol- 
ogy, summarizing,  in  concise  and  plain  language,  our  present 
knowledge  in  this  fundamental  branch  of  medicine.  It  is  true 
many  books  have  been  written  on  the  subject,  but  their  great 
brevity,  on  the  one  hand,  or  an  unnecessary  diffuseness  on  the 
other,  have  prevented  them  from  meeting  with  acceptance  at 
the  hands  of  physicians  and  students.  In  the  one  class  belong 
the  little  handbooks  of  Rutherford  and  Schaefer,  which  have 
done  much  to  simplify  and  therefore  popularize  histology,  but 
they  were  intended  for  beginners,  and  especially  students  doing 
class-work  under  the  laboratory  system  now  so  much  in  vogue. 
But  both  physician  and  student  need  something  of  wider  scope, 
and  they  have  been  compelled  to  turn  to  Klein  &  Smith, 
Strieker,  or  Frey1,  though  no  one  of  these  excellent  works  is 
thoroughly  adapted  to  their  wants. 

Apart  from  the  expense  of  the  two  former,  they  all  are 
deficient  in  matters  relating  to  human  histology. 

The  practical  experience  of  a  teacher  made  it  evident  also 
that  the  volume  to  fill  such  an  obvious  gap  should  take  the 
form  of  a  text-book.  And  the  present  time  seemed  opportune 
for  its  appearance,  since  we  have  latterly  made  much  positive 


IV  PREFACE. 

advance  in  liistological  studies,  while  liistologists  themselves 
are  now  more  of  one  mind  in  microscopical  matters.  That  such . 
a  book  should  appear  under  American  auspices  seemed  further 
to  be  eminently  proper,  as  we  have  in  various  parts  of  the  coun- 
try a  goodly  number  of  medical  men  who  are  either  engaged 
in  teaching  histology  or  in  studying  some  special  branch  of  it. 

The  advantages  of  utilizing  their  accumulated  experiences 
was  therefore  apparent  by  the  editor,  and  he  gladly  applied 
to  them  for  assistance  when  it  was  found  that  one  individual 
could  not  prepare  the  volume  within  a  reasonable  time  or 
in  a  manner  that  would  be  satisfactory.  It  is  hoped  that 
the  names  of  the  collaborators  furnish  a  sufficient  guarantee 
that  proper  representatives  of  American  histology  have  been 
selected.  In  some  respects  the  object  sought  for  has  not  been 
wholly  attained,  as,  for  example,  in  the  effort  to  separate 
purely  human  histology  from  the  comparative.  But  this  is 
impossible  at  the  present  time,  mainly  because  our  knowl- 
edge is  still  too  limited.  It  is  a  matter  of  regret,  also,  that  the 
original  illustrations  have  been  so  few  in  comparison  with  the 
total  number,  but  the  great  expense  attending  their  production 
would  not  warrant  any  one  in  attempting  much  in  this  direc- 
tion. Through  the  kind  co-operation,  however,  of  Messrs.  Wil- 
liam Wood  &  Co.,  the  editor  has  been  able  to  utilize  many 
excellent  cuts  that  were  in  their  possession. 

As  a  further  means  of  relieving  the  tedium  associated  with 
a  work  that  is  so  largely  descriptive,  the  various  authors  havo 
aimed  to  intersperse  here  and  there  throughout  the  text  mat- 
ters of  physiological  or  pathological  import.  Still,  intelligent 
practitioners  do  not  have  to  be  reminded  that  rational  thera- 
peutics has  found  a  substantial  support  in  the  revelations  of 
pathological  anatomy,  which,  in  turn,  rests  upon  histology, 


PREFACE.  y 

so  that  the  relation  between  microscopic  anatomy  and  the  sci- 
entific practice  of  medicine  is  readily  appreciated. 

Emanating  as  the  v.olume  does  from  American  sources,  the 
editor  finds  it  a  fitting  place  to  give  proper  space  to  American 
contributions,  and  the  reader  may  therefore  find  due  notice  of 
the  physiological  desquamation  of  blood-vessels,  considerations 
on  the  nature  of  nerve-termini,  matters  relating  to  the  intimate 
structure  of  the  striped  muscular  fibre  and  nerves,  with  the 
results  of  studies  on  the  structure  and  development  of  certain 
connective  substances,  and  novelties  in  microscopic  apparatus 
and  methods.  A  special  chapter  is  also  given  to  the  thick 
cutis  vera,  now  for  the  first  time  described  as  a  distinctive 
portion  of  the  skin.  In  it  will  be  found  detailed  the  discovery 
of  the  fat-columns,  which  are  calculated  to  explain  certain 
pathological  changes  that  have  been  imperfectly  understood. 

The  first  chapters  of  the  book  are  devoted  to  the  mechanism 
of  the  microscope,  and  to  certain  formal  methods  of  work  with 
which  the  beginner  should  be  familiar.  Of  the  illustrations, 
sixty-five  were  prepared  for  the  volume,  while  forty  have  never, 
it  is  believed,  appeared  in  book-form.  The  remainder  are 
mostly  from  the  manuals  of  Strieker  and  Frey. 

A  limited  number  of  bibliographical  references  have  been  in- 
serted where  it  was  thought  they  were  desirable  in  guiding 
the  reader  to  the  literature  of  the  subject.  For  the  prepara- 
tion of  these  tables  and  much  valuable  assistance,  the  editor 
here  desires  to  express  his  thanks  to  Dr.  E.  C.  Wendt,  of  this 
city. 

It  was  thought  best  to  omit  the  subject  of  optical  principles 
which  figure  so  conspicuously  in  some  of  our  histological 
manuals.  Those  who  wish  information  on  these  matters  are 
referred  to  any  of  the  standard  text-books  on  physics,  where 


VI  PEEFACE. 

tlie  subject  is  treated  at  greater  length  than  was  permissible  in 
the  present  instance. 

For  a  similar  reason,  and  also  because  it  would  prove  a 
needless  expense,  the  price-lists  of  instrument-makers  have 
been  omitted.  Full  particulars  relating  to  the  various  sorts  of 
microscopes  and  their  accessories  can  be  obtained  from  any 
of  the  leading  opticians,  who  from  time  to  time  issue  lists  con- 
taining ample  illustrations  of  the  most  recent  improvements 
in  all  that  pertains  to  practical  working  of  the  instrument. 

In  conclusion,  the  editor  finds  himself  compelled  to  reiter- 
ate the  well-worn  statement,  that  circumstances  over  which  he 
has  had  no  control  have  united  to  delay  the  press- work  of 
the  volume,  and  at  the  end  have  made  its  final  revision  rather 
hasty.  A  kind  indulgence  is  therefore  asked  for  any  error 
that  may,  through  oversight,  have  escaped  his  notice. 

T.  E.  S. 


TABLE   OF   CONTENTS. 


PART  I. 
CHAPTER  I. 

BY  THOMAS  E.  SATTERTHWAITE,  M.D. 

MATERIALS  REQUISITE  FOR  HISTOLOGICAL  WORK. — How  TO  USB  THE  MICRO- 
SCOPE.— TESTING  THE  MICROSCOPE. — ITS  USES Page     1 

Appliances  for  microscopic  work,  1.  Chemical  reagents,  3.  Illumina- 
tion, 4.  Stage  diaphragms,  5.  The  mirrors,  5.  Direct  and  oblique  light,  5. 
Arrangement  of  the  object,  6.  Kind  of  lens  to  use,  6.  How  to  keep  the 
instrument  clean,  7.  Magnifying  power  of  a  lens,  7.  How  to  estimate  the 
size  of  an  object,  8.  Testing  a  lens,  8.  How  to  illuminate  the  object,  9. 
Testing  the  eye-piece,  10.  Testing  high  lenses,  10.  Measuring  the  angle  of 
a  lens,  10. 

CHAPTER  II. 

BY  THOMAS  E.    SATTERTHWAITE,   M.D. 

METHODS  FOR  PREPARING  MICROSCOPIC  OBJECTS Page    12 

General  directions,  12.  To  prepare  fresh  objects  for  rapid  examination, 
13.  Ordinary  methods  of  preparing  tissues,  13.  Mailer's  fluid,  14.  Potas- 
sium bichromate  solution,  14.  Ammonia  bichromate  solution,  14.  Alcohol 
and  acetic  acid  mixtures,  14,  15.  Molybdate  of  ammonia,  15.  Solution  of 
osmic  and  chromic  acids,  15.  Alcohol  and  acetic  acid,  and  muriatic  acid 
solution,  15.  Method  of  hardening  the  brain,  15.  How  to  embed  speci- 
mens, 15.  Embedding  in  glycerine  and  tragacanth,  16.  The  hand  section- 
cutter,  16.  Freezing  section-cutters,  17.  Hailes'  microtome,  19.  The 
Vincent  microtome,  21.  Staining  fluids,  ammonia  carmine,  21.  Borax  car- 
mine, 22.  Double  staining,  22.  HEematoxylon  solutions,  23,  24.  Solutions 
for  multiple  staining,  24,  25.  Preparation  of  the  cornea,  25.  Triple  stain- 


Vlll  TABLE    OF    CONTENTS. 

ing,  26.  Double,  triple  and  quadruple  staining-,  26.  Bismark  brown,  26. 
Solution  of  alum  carmine,  27.  Naphthaline  yellow  for  bone,  27.  Methyl 
green  and  induline,  27.  Purpurine,  28.  French  archil,  28.  Alizarine,  28. 
Metallic  solutions,  staining  with  osmic  and  oxalic  acids,  28.  Chloride  of 
gold  and  lemon  juice,  28.  Nitrate  of  silver,  29.  Chloride  of  gold,  29. 
Osmic  acid,  29.  Methyl  green  for  waxy  change,  29.  Wickersheimer's 
liquid,  29.  Methods  of  injecting  the  blood-vessels,  30. 


CHAPTER  III. 
BY  THOMAS  E.   SATTERTHWAITE,   M.D. 

THE  BLOOD Page    34 

Red  corpuscles,  34.  Comparative  measurements  in  men  and  animals,  36. 
Number  of,  37.  Corpuscles  in  an  indifferent  fluid,  38.  Brownian  and 
amoeboid  movements,  39.  Heating  slide,  40.  Action  of  dilute  salt  solution, 
40.  Action  of  distilled  water — irrigation,  41.  Action  of  carbonic  acid  gas, 
42.  Action  of  acids,  43.  Action  of  alkalies,  44.  Action  of  electricity,  44. 
Exhibition  of  the  circulation,  45.  Internal  structure  of  red  corpuscles,  46. 
Development,  47.  White  corpuscles,  48.  Counting  corpuscles,  48.  Blood 
crystals,  53.  Haemoglobin,  53.  Hsemochromometer,  54.  Bibliography,  54. 


CHAPTER  IY. 

BY   THOMAS   E.    SATTERTHWAITE,   M.D. 

EPITHELIUM Page    56 

Ordinary  flattened  or  squamous  epithelium,  57.  Ciliated  epithelium,  58. 
Effect  of  reagents,  59.  Columnar  or  cylindrical  epithelium,  60.  Other  va- 
rieties, 61.  Structure  of  epithelial  corpuscles,  61.  Bibliography,  61. 

CHAPTER  Y. 

BY  THOMAS  E.    SATTERTHWAITE,    M.D. 

THE  CONNECTIVE  SUBSTANCE  GROUP. —Mucous  OR  GELATINOUS  TISSUE.— 
ADENOID  TISSUE. — NEUROGLIA. — FAT  TISSUE. — FIBROUS  TISSUE  PROP- 
ER.— CORNEAL  TISSUE. — INTERMUSCULAR  TISSUE. — TENDON  TISSUE. — 

ELASTIC  TISSUE , Page    62 

Connective  substances  in  general,  62.  Mucous  or  gelatinous  tissue,  63. 
Development  of  fibrous  tissue,  64,  65.  Fibrous  tissue,  6(5.  Adenoid  tissue, 
69.  Neuroglia,  70.  Tendon  tissue,  72.  Fat  tissue,  73.  Intermuscular 
tissue,  74.  Corneal  tissue,  75.  Elastic  tissue,  77.  Pavement  endothe- 
lium,  80.  Bibliography,  81. 


TABLE    OF    CONTENTS.  IX 

CHAPTER  YL 

BY  THOMAS   E.    SATTERTHWAITE,   M.D. 

THE  CONNECTIVE-SUBSTANCE  GROUP  (Continued). — CAKTILAGE Page    82 

Hyaline  cartilage,  82.  Parenchymatous  cartilage,  83.  Division  of  the 
corpuscle,  84.  Calcifications,  84.  Methods  of  studying  hyaline  cartilage, 
84.  Yellow  elastic  cartilage,  85.  Fibrous  cartilage,  86,  Structure  of  cor- 
puscle, 87.  Bibliography,  88, 

CHAPTER  YIL 

BY  THOMAS  E.    SATTERTHWAITE,   M.D. 

TnE  CONNECTIVE-SUBSTANCE  GROUP  ( Continued). — BONE Page    89 

Compact  tissue,  89.  Ossein,  89.  Bone-corpuscles,  90.  Haversian  sys- 
tem, 90.  Preparation  of  dry  bone,  92.  Preparations  of  decalcified  bone,  92. 
Sharpey's  fibres,  94.  Cancellous  tissue,  94.  Marrow,  95.  Periosteum,  95. 
Development  of  bone,  96 ;  through  cartilage,  97 ;  from  membrane,  de- 
velopment and  absorption,  99.  Howship's  lacunae,  100.  Formation  of  cal- 
lus, 100.  Bibliography,  101. 

CHAPTER  YIII. 

BY  THOMAS  E.    SATTERTHWAITE,  M.D. 

THE  TEETH Page  102 

The  enamel,  102.  Dentine  or  ivory,  103.  Dentinal  globules,  104.  Cement, 
105.  Pulp,  105.  Development  of  teeth,  105.  Primary  enamel  organ,  107. 
Development  of  enamel,  108.  Bibliography,  108. 

CHAPTER  IX. 

BY  THOMAS  E.    SATTERTHWAITE,  M.D. 

GENERAL  HISTOLOGY  OP  THE  NERVOUS  SYSTEM Page  109 

Nerve-fibres,  109.  Myelinic  fibres,  109.  Staining  in  picro-carmine,  111. 
Staining  with  silver,  112.  Staining  with  osmic  acid,  113.  Semi-desicca- 
tion, 113.  Transverse  sections  of  myelinic  nerves,  114.  Preparation  by 
ammonia  bichromate,  115.  Modern  conceptions  of  myeliuic  nerves,  116. 
Fibres  of  Remak,  preparations  in  osmic  acid  and  picro-carmine,  118.  Prep- 
arations of  Remak's  fibres  in  hsematoxylon,  118.  Ganglionic  bodies,  119. 
Ganglia  of  the  cranial  and  spinal  nerves,  120.  Gasserian  ganglion,  120. 
Ganglionio  bodies  of  the  spinal  cord,  120.  Brain,  121.  Sympathetic,  121. 
Meissner's  plexus,  122.  Auerbach's  plexus,  123.  Termination  of  nerves, 
123.  Tactile  corpuscles,  124.  Pacinian  bodies,  124.  Nerve-terminations 
in  muscle,  125  ;  in  epithelium,  126.  Connective  tissue  of  nerves,  126. 
Bibliography,  127 


TABLE    OF    CONTENTS. 


PART    II. 


CHAPTER  X. 

BY  THOMAS  D  WIGHT,   M.D. 

MUSCULAR  FIBRE. Page  128 

Involuntary  muscular  fibre,  128.  Voluntary  muscular  fibre,  130.  Physi- 
ological attributes,  134.  Nuclei  and  muscle  corpuscles,  136.  Conclusions, 
137.  Peculiarities  of  voluntary  muscles,  138.  Termination  of  muscle  in 
tendon,  139.  Muscular  fibre  of  the  heart,  140.  Bibliography,  140. 


CHAPTER  XL 

BY   EDMUND   C.    WENDT,   M.D. 

THE  BLOOD-VESSELS Page  14</ 

Capillary  blood-vessels,  142.  Vascular  endothelium,  143.  Capillaries 
proper,  144.  Genesis,  reproduction,  and  regeneration  of  capillaries,  150. 
Arteries,  151.  Veins,  155.  Peculiar  vascular  structures,  158.  Blood-vas- 
cular glands,  vascular  plexuses,  158.  Intercarotid  gland,  160.  Corpora 
cavernosa,  160.  Vasa  vasorum,  lymphatics,  and  nerves,  161.  Bibliography, 
162. 

CHAPTER  XII. 

BY  W.    R.   BIRDSALL,   M.D. 

THE  LYMPHATIC  SYSTEM Page  163 

Modern  views  of,  relative  to  connective  tissue,  163.  General  histology, 
164.  Lymphatics  of  the  mesentery,  165.  Klein's  studies  on  the  omentum, 
166.  Perilymphangeal  nodules,  167.  Development  of  fat-tissue,  168.  Lym- 
phatic radicles,  168.  Artificial  injection  of  lymphatics,  169.  Endothelium 
and  stomata.  169.  False  stomata,  170,  171.  Intimate  structure  of  lym- 
phatic vessels,  172.  Variations  in  shape,  173.  Topographical  peculiarities, 
174.  Thoracic  duct,  174.  Subarachnoid  and  subdural  spaces,  175.  Lym- 
phatics of  tendons,  175.  Lymphatic  glands,  175.  Nerves  of  lymphatic 
nodes,  179.  Injection  of  a  lymphatic  gland,  179.  Method  of  studying,  179. 
Ranvier's  method,  180.  Other  methods  of  injecting  glands,  180.  Bibli- 
ography, 182. 


TABLE    OF    CONTENTS.  XI 

CHAPTER  XIII. 

BY  A.    MAYER,   M.D. 

THE  LIVER  AND  BILIARY  APPARATUS Page  183 

Hepatic  lobules,  183.  Blood-vessels,  186.  Connective  tissue,  188.  Liver- 
cells,  189.  Larger  biie -ducts,  191.  Glands  of  the  ducts,  191.  Capillary 
bile-ducts,  192.  Do  the  bile-capillaries  possess  walls  ?  196.  Gall-bladder, 
197.  Lymph-vessels  of  the  liver,  198.  Nerves,  199.  Bibliography,  199. 


CHAPTER  XIY. 

BY   A.    MAYER,   M.D. 
THE  KIDNEY Page  201 

General  structure,  201.  Renal  tubules,  203.  Their  epithelium,  206.  The 
loops,  209.  Their  epithelium,  210.  Intercalated  portions,  211.  Collecting 
tubules,  211.  Their  epithelium,  21 1.  Blood-vessels  of  the  kidney,  213.  In- 
jecting the  kidney,  214.  Kidney  stroma,  215.  Nerves,  lymphatics,  capsule, 
calyx,  216.  Natural  injection  by  the  sulphindigate  of  soda,  216.  Bibliog- 
raphy, 222. 

CHAPTER  XY. 

BY  J.   HENRY  C.   SIMES,   M.D. 

MALE  EXTERNAL  AND  INTERNAL  ORGANS  OP  GENERATION,  WITH   THEIR 
GLANDULAR  APPENDAGES Page  223 

Penis,  223.  Urethra,  225.  Co wper's  glands,  227.  Prostate,  227.  Testi- 
cles, 229.  Tunica  vaginalis,  230.  Hydatid  of  Morgagni,  231.  Vas  defe- 
rens,  232.  Seminal  vesicles,  235.  Bibliography,  238. 


CHAPTER  XYI. 

BY  J.    HENRY  C.   SIMES,   M.D. 

FEMALE  EXTERNAL  AND  INTERNAL  ORGANS  OF  GENERATION,  WITH  THEIR 
GLANDULAR  APPENDAGES.  —PLACENTA Page  240 

Labia  majora,  240.  Labia  minora,  240.  Clitoris,  240.  Vestibule,  241. 
Glands  of  Bartholine,  241.  Hymen,  241.  Vagina,  241.  Urethra,  242. 
Uterus,  243 ;  Mucous  membrane  of,  243.  Ovula  Nabothi,  244.  Fallopian 
tubes,  246.  Ovary,  246.  Graafian  follicles,  248.  Parovariuni,  350.  Pla- 
centa, 251.  Bibliography,  251. 


Xll  TABLE    OF    CONTENTS. 

CHAPTER  XYII. 

BY  BENJAMIN  F.   WESTBROOK,  M.D. 

THE  RESPIRATORY  TRACT Page  253 

Larynx,  !i53.  Ligaments  of,  253.  Cartilages,  254.  Epiglottis,  255. 
Mucous  membrane,  255.  Trachea  and  primary  bronchi,  257.  Smaller  bron- 
chi and  lungs,  259.  Plenra,  265.  Lymphatics  of,  267.  Pleural  append- 
i,  267.  Bibliography,  267. 


CHAPTER  XVIII. 

BY  A.    R.  ROBINSON,    M.D. 

THE  SKIN Page  269 

General  plan  of  arrangement,  269.  Structure,  270.  Different  layers, 
271.  Epidermis,  271.  Rete  Malpighii,  271.  Granular  layer,  274.  Stratum 
lucidum,  274.  Corneous  layer,  274.  Subcutaneous  connective-tissue  layer, 
275.  Pacinian  corpuscles,  corium,  277.  Blood-vessels,  279.  Nerves,  279. 
Tactile  corpuscles,  280.  Sweat-glands,  282.  Muscles,  287.  The  hair,  288. 
Nails,  293.  Bibliography,  295. 

CHAPTER  XIX. 

BY  R.   W.    AMIDON,   M.D. 

THE  CENTRAL  NERVOUS  SYSTEM Page  296 

Spinal  dura  mater,  296.  Spinal  arachnoid,  297.  Spinal  pia  mater,  297. 
General  histology  of  the  spinal  cord,  298.  Nerve-elements  of  the  cord,  299. 
Special  studies  in  different  portions  of  the  cord,  301.  Medulla  oblongata, 
307.  Olivary  body,  310.  Cerebellum,  317.  Cerebral  ganglia,  319.  Cere- 
bral ventricles,  319.  Cerebral  cortex,  321.  Structure  of  cortex,  323.  Bib- 
liography, 325. 

CHAPTER  XX. 

BY  C.    H.   WILLIAMS,   M.D. 

THE  EYE Page  328 

Eyelids,  328.  Eyelashes,  328.  Tarsus,  329.  Meibomian  glands,  329. 
Conjunctiva,  330.  Cornea,  331.  Solera,  337.  Vitreous  layer,  339.  Ciliary 
body,  340.  Retina,  343.  Lens,  350.  Lachrymal  gland,  351.  Bibliography, 
352. 

CHAPTER  XXL 

BY  W.    F.  WHITNEY,  M.D.,  AND  CLARENCE  J.    BLAKE,  M.D. 

THE  EAR Page  353 

External  ear,  353.  Middle  ear,  355.  Eustachian  tube,  355.  Internal 
ear,  357.  Membranous  labyrinth,  358.  Cochlea,  362.  Bibliography,  367. 


TABLE    OF   CONTENTS.  X1U 


PART  III. 
CHAPTER  XXII. 

BY  D.  BRYSON  DELAVAN,   M.D. 

THE  NASAL  FOSSAE,  PHARYNX,  AND  TONSILS Page  368 

Vestibulum  nasi,  368.  Respiratory  region,  368.  Olfactory  region,  370. 
Olfactory  nerves,  372.  Bowman's  glands,  372.  Pharynx,  373.  Tonsils, 
373.  Bibliography,  375. 

CHAPTER  XXIII. 

BY  D.    BRYSON  DELAVAN,    M.D. 

THE  MOUTH  AND  TONGUE Page  377 

Tunica  propria,  377.  Blood-vessels,  379.  Lymphatics,  379.  The  tongue, 
380.  Papillae,  380.  Taste-goblets,  381.  Bibliography,  384. 

CHAPTER  XXIV. 

BY  EDMUND  0.    WENDT,   M.D. 

THE  ALIMENTARY  CANAL Page  386 

(Esophagus,  386.  Stomach,  388.  Small  intestine,  394.  Large  intestine, 
400.  Rectum,  401.  Bibliography,  402. 

CHAPTER  XXY. 

BY  C.   L.  DANA,  M.D. 

THE  SPLEEN,  PANCREAS,    THYMUS,  THYROID,  AND  PINEAL  GLANDS,  AND 
PITUITARY  BODY Page  403 

The  spleen— coats,  403,  404.  Malpighian  corpuscles,  404.  Pulp,  406. 
Blood-vessels,  407.  Lymphatics,  409.  Nerves,  409.  Development,  409. 
Pancreas — excretory  duct,  411.  Blood-vessels,  411.  Lymphatics,  411. 
Nerves,  411.  Development,  411.  Thymus  gland,  412.  Capsule,  412.  Fol- 
licles, 412.  Central  canal,  414.  Blood-vessels,  lymphatics,  development,  414. 
Thyroid  body,  415.  Blood-vessels,  416.  Lymphatics,  416.  Nerves,  416. 
Pineal  gland,  417.  Pituitary  body,  417.  Bibliography,  418. 


XIV  TABLE    OF    CONTENTS. 

CHAPTER  XXYI. 

BY  J.  COLLINS  WARREN,  M.D. 

THE  THICK  CUTIS  VERA page  420 

Fat-columns,  421.     Blood-vessels,  423.     Lymphatics,  424. 

CHAPTER  XXVII. 

BY  EDMUND  C.  WENDT,  M.D. 

URINARY  EXCRETORY  PASSAGES.— SUPRARENAL  CAPSULES Page  428 

Renal  pelvis,  428.  Ureters,  429.  Bladder,  430.  Suprarenal  capsules, 
431.  Bibliography,  437. 

CHAPTER  XXVIIL 

BY  W.  H.   PORTER,  M.D.,  AND  E.    C.   WENDT,  M.D. 

MAMMARY  GLAND Page  439 

General  considerations,  439.  Nipple,  440.  Galactophorous  ducts,  441. 
Milk  reservoirs.  441.  Areola  mammae,  442.  Arteries,  442.  Lymphatics, 
443.  Nerves,  443.  Structure  of  expanded  gland,  444.  Of  involuted  gland, 
446.  Rauber's  views,  450.  Corpuscles  of  Donne,  450.  Milk,  451.  Devel- 
opment, 452.  Plan  of  histological  study,  455.  Bibliography,  456. 


MANUAL   OF    HISTOLOGY 


AND 


HISTOLOGICAL  METHODS. 


CHAPTER   I. 

MATERIALS  REQUISITE  FOE  HISTOLOGICAL  WORK— HOW  TO  USE 
THE  MICROSCOPE— TESTING  THE  MICROSCOPE— ITS  USES. 

VERY  little  apparatus  and  few  reagents  are  essential  for  gen- 
eral histological  work.  Such  as  are  really  needed  may  be  so 
arranged  as  to  fit  in  a  box  or  bag,  that  can  be  carried  in  the 
hand.  First  of  all,  the  student  should  be  provided  with  a 


FIG.  2. 


FIG.  1. 


FIG.  3. — Curved  Iris  Scissors. 


pair  of  small  forceps,  with  either  curved  or  straight  points 
(Figs.  1,  2),  according  to  individual  fancy ;  a  pair  of  delicate 
curved  iris  scissors  (Fig.  3) ;  a,  few  pipettes ;  a  glass  rod  or 


2  MANUAL    OF    HISTOLOGY. 

two  ;  a  spoon  (Fig.  4)  for  lifting  sections  of  tissues  from  the 
fluids  in  which  they  have  been  immersed  ;  a  pair  of  needles 
(Fig.  5)  in  handles  for  teasing  or  tearing  tissues  ;  (the  handles 
used  for  crochet  needles,  or  the  pin-slides  sold  by  jewelers, 
may  be  fitted  with  ordinary  milliners  needles,  which  are  long, 
delicate,  and  flexible,  and  therefore  well  adapted  for  this 


FIG.  4. 


FIG.  5.  — Microscopic  Needle-holder. 


work)  a  sable  or  camel's  hair  brush  for  removing  cellular 
elements,  so  as  to  bring  particular  parts  into  prominence  ;  bibu- 
lous paper  ;  a  sharp  knife  (Fig.  6)  for  cutting  thin  sections  ; l 

1  For  this  purpose  the  razors  made  by  Le  Coultre,  in  Geneva,  have  been  highly 
recommended,  but  good  knives  may  be  obtained  of  almost  any  cutler  ;  indeed,  most 
of  the  makers  of  surgical  instruments  furnish  them ;  they  are  usually  flat  on  one 
side  and  slightly  concave  on  the  other. 


MATERIALS    REQUISITE    FOR    HISTOLOGICAL    WORK.  3 

five  or  six  sJiallow  porcelain  dishes,  ounce  gallipots,  with  flat 
bottoms,  in  which  to  soak  the  tissues  when  they  have  been  cut ; 
glass  slides  for  mounting  specimens  (the  ordinary  size  is  3  x  1 
inch)  ;  thin  glass  or  mica  covers  (squares  or  circles)  for  cover- 
ing the  specimens  (three-quarters  of  an  inch  is  a  good  diameter). 

Mica  covers  are  much  cheaper  than  glass,  and  are  suitable  for  rapid  work 
and  when  it  is  not  desirable  to  make  permanent  preparations. 


FIG.  8.— Beer's  Cataract  Knife. 

In  addition,  a  small  Beer's  cataract  knife  (Pig.  8)  will  be 
found  useful  for  puncturing  vessels  and  hollow  organs  to  obtain 
samples  of  their  fluid  contents.  All  of  these  articles  may  easily 
be  contained  in  the  drawer  of  a  box  10  x  12  inches  in  size  ; '  the 
upper  portion  will  hold  the  necessary  reagents.  These  latter 
should  comprise  a  small  amount  of  a  three-fourths  per  cent, 
aqueous  solution  of  sodium  chloride,  about  an  equal  amount 
of  distilled  water,  dilute  acetic  acid,  glycerine,  and  iodized  se- 
rum;* a  fluid  ounce  of  each  will  be  all  that  is  necessary,  and 
for  convenience  of  use  they  may  be  put  in  corked  bottles  pro- 
vided with  capped  pipettes  passing  through  the  corks.  The 
vials  and  perforated  corks  may  be  obtained  of  almost  any 
apothecary.  The  cap  being  of  rubber,  very  small  quantities 
of  the  fluid  can  be  withdrawn  from  the  bottle  and  pressed  out 
as  desired,  either  upon  the  slide  or  otherwise. 

Other  reagents  required  are  oil  of  cloves  in  a  two-ounce 
stoppered  bottle ;  dammar  varnish  or  Canada  balsam,  each  in 
a  capped  bottle  (Fig.  7),  containing  a  glass  rod  ;  a  solution  of 
logwood,  and  another  of  borax  carmine,3  in  ordinary  glass 
stoppered  two-ounce  bottles,  and  a  small  vial  of  asphalt  or 
some  similar  cement.  It  will  be  useful,  in  addition,  to  have  a 
small  bottle  (4  oz.)  of  absolute  alcohol,  another  (8  oz.)  of  com- 
mercial alcohol,  some  Muller's  fluid3  (8  oz.),  and  a  solution  of 
the  bichromate  of  potassium  (gr.  xv. —  5  ]•)• 

1  T.  H.  McAllister,  optician,  No.  49  Nassau  Street,  New  York  City,  has  made  one 
for  me  which  answers  the  purpose  satisfactorily.     Miller  Bros. ,  No.  69  Nassau  Street 
and  1213  Broadway,  New   York  City,  also   make   and  furnish  cases  for  the  same 
purpose. 

2  Formula  in  the  chapter  on  General  Methods. 

3  Ibid. 


MANUAL    OF    HISTOLOGY. 

good  liistological  work  can  be  done  without  a  note-book 
to  record  the  results  of  observation.  All  such  memoranda  will 
be  very  useful  for  subsequent  reference.  A  lieating  slide,  a 
gas  chamber  and  a  slide  arranged  for  conducting  electric  cur- 
rents may  also  be  desirable.  They  will  be  described  in  the 
chapter  on  the  Blood. 

The  following  substances  that  cannot  be  contained  in  a  box, 
and  are  necessary  in  some  forms  of  microscopic  work,  may  be 
mentioned:  osmic  acid  (1  per  cent.),  nitric  acid  (C.  P.),  distilled 
water,  olive  oil,  caustic  soda  or  potash,  chloride  of  gold  (i  per 
cent,  sol.).1 

It  is  also  very  convenient  to  have  at  hand  a  short  wooden 
rule  which  is  divided  into  inches  and  tenths  of  an  inch.  The 
stage  micrometer  is  also  equally  necessary.  Other  accessory 
materials  will  be  described  in  their  proper  places. 


HOW  TO  USE  THE  MICROSCOPE.8 

Illumination. — When  the  instrument  is  ready  for  use  it 
should  be  placed  upon  a  firm  and  rather  low  table,  near  a 
window,  which  does  not  receive  the  direct  rays  of  the  sun.  If 
daylight  is  not  to  be  obtained,  a  small  kerosene  hand-lamp  will 
answer  sufficiently  well  for  illuminating  purposes.  The  flame 
should  be  on  a  level  with  the  reflecting  mirror  of  the  micro- 
scope, and  quite  near  it.  Sometimes  a  condenser  is  interposed, 
but  this  is  rarely  necessary,  and,  indeed,  it  may  be  said  that  it 
never  comes  into  use  in  histological  work. 

A  thin  sheet  of  blue  glass  may  sometimes  be  found  to  assist 
the  eye  when  artificial  illumination  is  used,  as  the  light  is  made 
white.  Some  microscope  makers  furnish  with  their  instru- 
ments a  set  of  blue  glasses  varying  in  color  from  very  light  to 
dark  blue.  They  are  rarely  needed,  as  the  eye  soon  becomes 
accustomed  to  continuous  work  for  long  sittings,  even  when 
strong  light  is  employed.  Those  who  work  much  with  the 
microscope  keep  both  eyes  open,  and  use  first  one  and  then 

1  Formula  in  the  chapter  on  General  Methods. 

2  It  is  presumed  that  students  engaging  in  histological  work  are  more  or  less 
familiar  with  the  mechanism  of  the  microscope.       For  this  reason  the  subject  of 
optical  principles  and  the  description  of  the  different  parts  of  a  microscope  are  omitted 
here.     Those  who  may  wish  special  information  on  these  points  are  referred  to  Ap- 
pendix A. 


HOW    TO    USE    THE    MICROSCOPE.  5 

the  other.  Some  find  it  a  great  assistance  to  direct  the  un- 
engaged eye  upon  a  dark  object,  such  as  a  blackened  card, 
which  they  fasten  to  the  tube  of  the  instrument  near  its  top. 

As  it  is  desirable  that  the  lamp  should  only  illuminate  the 
reflector,  a  great  many  ingenious  contrivances  have  been  made 
to  cut  off  the  superfluous  light.  For  this  purpose  some  micros- 
copists  interpose  a  piece  of  thin  board,  or  a  thick  card,  having 
a  circular  opening  between  the  lamp  and  the  reflector. 

Stage  diapJiragms. — When  the  pencil  of  light  has  been 
reflected  from  the  mirror  upon  the  opening  in  the  stage,  it  is 
plain  that  a  larger  or  smaller  amount  of  light  will  pass,  accord- 
ing to  the  size  of  the  opening.  The  appliances  that  regulate 
this  matter  are  called  stage  diaphragms — sometimes  they  are 
simply  cylindrical  tubes  with  capped  upper  extremities,  each 
tube  being  provided  with  caps  of  varying  aperture.  The  tubes 
are  pushed  into  the  stage  from  beneath.  When  polished  they 
undoubtedly  aid  in  converging  the  light  upon  the  aperture. 
Other  diaphragms  are  simply  round  holes  in  a  circular  revolving 
plate  which  is  set  into  the  stage. 

The  diameters  of  the  apertures  vary  from  that  of  a  pin's 
point  to  about  three-fourths  of  an  inch  or  even  more. 

The  revolving  diaphragms  have  now  come  into  general  use, 
because  they  work  simply  and  efficiently.  Mr.  Wale  has  de- 
vised one  that  is  extremely  ingenious.  It  has  the  advantage 
of  a  cylindrical  diaphragm,  in  so  far  as  it  converges  the  pencil 
of  light  upon  the  diaphragmatic  opening,  while  the  size  of  the 
opening  is  regulated  by  the  action  of  a  single  thumb-screw.1 
It  acts  as  the  iris  does  in  enlarging  or  diminishing  the  pupil, 
from  which  its  name,  the  iris  diaphragm. 

TJie  mirrors. — Of  these  there  should  be  two,  cms  plane  when, 
a  diffuse  light  is  needed  ;  the  other  concave  for  a  concentrated 
beam.  The  latter  is  frequently  used,  the  former  seldom. 

Direct  and  oblique  light. — Thus  far  the  descriptions  have 
applied  to  direct  light,  and  it  is  the  only  kind  much  used  in 
histological  work.  In  testing  a  lens,  however,  as  with  a  diatom, 
it  is  often  necessary  to  use  oblique  light  in  order  -to.resolve  a 
line  or  series  of  lines.  In  such  cases  the  aperture  in  the  stage 
should  be  made  as  large  as  possible,  and  the  mirror,  concave  or 
plane,  is  to  be  carried  well  up  under  the  stage,  to  the  left  or 

1  See  Appendix  A. 


6  MANUAL    OF    HISTOLOGY. 

right,  so  that  the  pencil  of  light  may  be  thrown  across  the 
object.  By  this  means,  little  inequalities  of  the  surface  which 
would  be  invisible  under  direct  light  are  clearly  demonstrated. 
The  poorer  lenses,  however,  are  those  which  necessitate  oblique 
light.  When  reference  is  made  to  the  definition  of  the  lens, 
direct  light  is  intended. 

Arrangement  of  tlie  object. — When  the  object  is  to  be  ex- 
amined, it  should  be  placed  upon  the  glass  slide,  which  is  usu- 
ally one  by  three  inches  in  superficial  measurement,  and  as 
thin  as  is  compatible  with  the  usages  to  which  it  is  put  in 
ordinary  microscopic  work.  The  glass  should  be  white  in  color, 
and  free  from  any  imperfections  that  can  be  detected  by  the  eye. 
Usually  a  drop  or  two  of  water,  a  drop  of  glycerine,  or  a  drop 
of  water  and  glycerine  in  equal  parts,  is  placed  upon  the-  slide. 

The  object  is  then  immersed  in  the  liquid.  It  takes  some 
little  time  for  the  fluid  to  permeate  the  specimen,  so  that  it  is 
ready  for  study.  When  pure  glycerine  is  used  fully  ten  minutes 
will  generally  elapse  before  the  specimen  is  transparent.  A 
covering  glass  is  then  cautiously  let  fall  upon  the  liquid,  care 
being  taken  that  no  bubble  of  air  enters.  The  cover  is  then 
pressed  down.  In  such  cases,  when  the  object  is  studied  with 
high  powers,  the  cover  will  often  slowly  rise  and  separate  itself 
from  the  slide,  so  that  the  forceps  or  the  finger  may  be  neces- 
sary to  press  it  back.  This  inconvenience  is  obviated  by  paint- 
ing a  little  Canada  balsam  or  cement  around  the  edge  of  the 
cover  so  as  to  hold  it  down. 

The  kind  of  a  lens  to  be  used. — For  the  first  examination  a 
low  objective  should  be  used,  with  a  medium,  not  short,  eye- 
piece. The  tube  should  then  be  carried  down  until  the  object 
comes  within  the  focus.  Low  powers  should  always  be  used 
at  first,  because  they  give  a  good  idea  of  the  object  in  its  gen- 
eral features. 

Then  the  tube  may  be  withdrawn,  and  a  higher  power  sub- 
stituted, and  so  on,  until  the  specimen  has  been  studied  in  all 
its  details.  A  convenient  accessory  is  now  made  by  most  of 
the  instrument  makers;  it  is  a  "nose-piece" — a  brass  attach- 
ment which  is  screwed  into  the  end  of  the  tube,  and  carries  two 
or  more  lenses.1 


1  The  double  angular  nose-piece  made  by  Schrauer,  46  Nassau  Street,  costs 
the  triple,  $20  ;  all  of  the  microscope  makers  are  now  prepared  to  furnish  them. 


TESTING   THE    MICROSCOPE ITS    USES.  7 

The  first  named  is  usually  fitted  with  a  f  and  a  £  inch  lens  ; 
in  addition  to  these  a  TV  immersion  may  be  used  for  the  triple 
nose-piece. 

How  to  keep  the  instrument  clean. — After  using  the  instru- 
ment it  should  always  be  wiped  dry,  as  it  is  damp  from  the 
moisture  of  the  breath  and  hands.  The  lenses  should  be  re- 
turned to  their  cases,  and,  if  necessary,  the  surfaces  are  to  be 
rubbed  off  with  a  bit  of  soft  chamois  skin  or  fine  linen.  Water 
will  remove  almost  all  the  dirt  from  the  anterior  lens,  but  occa- 
sionally it  may  be  necessary  to  use  alcohol.  In  such  cases  but 
very  little  is  requisite,  as  it  may  penetrate  behind  the  anterior 
lens  and  dissolve  the  Canada  balsam  that  cements  the  different 
portions  together. 

It  is  well  for  the  student  to  familiarize  himself  at  first  with 
certain  common  objects  that  are  apt  to  be  met  with  in  all 
forms  of  microscopic  work,  such  as  the  little  foreign  substances 
that  go  to  make  up  the  dust  of  rooms ;  these  include  minute 
bits  of  wood,  cotton  and  linen  fibres,  particles  of  wool,  hairs  of 
various  animals,  feathers,  etc. 

The  imperfections  in  the  glass  should  also  be  noted,  and 
especially  the  curious  red  figures  sometimes  resembling  butter- 
fly wings,  caused  by  an  accumulation  in  the  flaws  of  the  glass 
of  a  red  substance — the  red  oxide  of  iron — used  by  manufac- 
turers in  polishing  glass.  These  red  figures  are  often  wonder- 
fully alike,  and  have  given  rise  to  singular  errors  among  micro- 
scopical workers. 


TESTING  THE  MICROSCOPE— ITS  USES. 

Magnifying  power  of  a  lens. — To  determine  the  actual 
magnifying  power  of  a  lens  in  combination  with  the  particular 
eye-piece  that  happens  to  be  in  use,  the  ordinary  method  is  as 
follows : 

The  glass  stage  micrometer,  which  is  ruled  off  into  tenths, 
hundredths,  and  thousandths  of  an  inch,  is  placed  upon  the 
stage  and  focussed.  This  having  been  done,  the  wooden  rule, 
which  we  have  already  alluded  to  and  which  is  divided  into 
inches  and  tenths  of  an  inch,  is  laid  alongside  of  the  micro- 
meter-slide. 

One  eye,  looking  outside  of  the  tube,  reads  off  the  number 


MANUAL    OF   HISTOLOGY. 

of  divisions  of  the  wooden  rule  corresponding  to  a  single  divi- 
sion of  the  micrometer  slide  as  seen  with  the  other  eye  directed 
through  the  tube  of  the  microscope. 

By  this  method  of  double  vision,  as  it  were,  a  comparison  is 
instituted  between  the  two  rules,  and  the  ratio  that  one  bears 
to  the  other  may  be  estimated. 

Suppose,  for  example,  that^V  o  of  an  inch  on  the  scale  of  the 
stage  micrometer  is  equal  to  fV  of  an  inch  on  the  wooden  rule. 
The  ratio  of  ToVg-  to  T27  will  represent  the  magnifying  power 
of  that  particular  combination.  Reducing  these  fractions  to 
a  common  denominator  they  stand  to  one  another  as  1  to  200. 
The  object  has  therefore  been  magnified  two  hundred  times. 

With  a  short  eye-piece  the  power  is  greater  and  it  increases 
in  proportion  as  the  tube  is  drawn  out.  It  is  customary  how 
ever  to  assume  a  certain  length  of  the  draw-tube  as  the  stand- 
ard :  this  is  twenty-five  centimetres  or  about  eight  inches. 

How  to  estimate  the  size  of  an  object- — To  estimate  the  size 
of  an  object  is  a  much  easier  task.  Place  the  stage  micrometer 
upon  the  stage  of  the  microscope  and  then  slip  the  micrometer 
eye-piece  into  the  draw-tube.  The  micrometer  eye-piece  is 
simply  an  ordinary  ocular  with  a  glass  cover  fitted  into  the 
diaphragm.  The  micrometer  consists  of  a  series  of  parallel 
lines  ruled  across  it  at  regular  distances  apart.  By  focussing 
the  lines  on  the  stage  micrometer  one  may  readily  count  the 
actual  fractions  of  an  inch  corresponding  to  a  single  division 
in  the  micrometer  eye-piece. 

Thus,  for  example,  if  we  find  that  a  single  division  of  the 
micrometer  eye-piece  corresponds  to  ToVfr  of  an  inch,  and  that 
a  lymphoid  corpuscle  covers  half  a  division,  its  diameter  is 
necessarily  -g-faf  of  an  inch. 

Testing  a  lens. — A  lens  should  be  free  from  certain  defects, 
as  we  have  already  stated.  First  of  all  it  should  have  no 
spherical  aberration ;  the  objects  seen  upon  the  edge  of  the 
field  should  be  sharply  defined,  and  all  objects  having  parallel 
sides  should  appear  as  such.  In  other  words,  they  should  not 
be  distorted. 

Secondly,  they  should  have  no  color  or,  at  least,  as  little 
as  possible.  This  defect,  however,  has  never  been  entirely 
overcome ;  some  glasses  are  over-corrected  and  then  the  pre- 
vailing color  is  blue  ;  others  are  under-corrected  and  then  the 
prevailing  color  is  red. 


TESTING    THE     MICROSCOPE — ITS    USES.  9 

It  is  a  matter  of  some  indifference  which  color  prevails. 
These  defects  are  best  seen  by  observing  a  bubble  of  air  in  a 
fluid  specimen.  The  prevailing  color  is  seen  at  the  periphery 
of  the  bubble. 

Thirdly,  all  objects  in  the  field  should  appear  with  equal 
distinctness,  whether  at  the  periphery  or  in  the  centre.  If  a 
fine  powder,  such  as  lycopodium  be  strewn  over  the  field,  the 
granules  should  be  seen  as  distinctly  at  the  edges  as  at  the 
centre  ;  an  ordinary  thin  section  of  any  microscopic  object  will 
also  exhibit  this  defect,  if  it  exist. 

Fourthly,  the  glasses  should  have  good  penetration.  This 
enables  the  observer  to  see  the  general  aspect  of  bodies  better, 
though  it  may  not  make  him  see  objects  quite  as  sharply  ;  the 
former  depending  upon  a  large  angle  of  aperture,  and  the  latter 
(definition)  upon  a  small  one. 

To  be  able  to  have  at  the  same  time  both  great  resolving 
and  great  defining  power  is  the  highest  desideratum,  and  it  has 
been  the  merit  of  our  American  makers  to  increase  the  angle 
of  aperture  and  still  maintain  a  high  defining  power. 

For  ordinary  histological  purposes,  a  lens  that  will  show 
the  oscillatory  movement  in  the  mucous  or  salivary  corpuscles 
is  sufficiently  high  for  practical  purposes.  This  is  accomplished 
by  the  ordinary  student's  one-fifth  of  Grunow,  for  example. 
If,  however,  we  are  studying  the  delicate  intercellular  sub- 
stance of  the  brain  and  connective-tissue  corpuscles,  bacteria, 
etc.,  a  somewhat  higher  power  is  needed. 

For  such  studies  it  is  desirable  to  have  an  immersion  lens,  such  as  the  No.  10 
or  12  Hartnack  or  Prazmowski,  or  a  ^  or  ^  of  other  good  makers,  such  as 
Wale,  Tolles,  etc. 

In  using  these  high  powers  it  is  necessary  to  place  a  single  drop  of  water 
on  the  anterior  lens  and  depress  the  tube  imtil  the  drop  touches  the  circle 
or  cover.  The  drop  of  water  utilizes  light  that  would  otherwise  be  lost,  mag- 
nifies slightly,  and  corrects,  so  that  the  image  is  made  brighter  and  more 
distinct. 

The  new  oil  immersion  of  Zeiss  is  highly  recommended  by  Woodward  of 
Washington.  In  using  such  a  lens,  a  drop  of  oil  is  substituted  for  water.  We 
are  hardly  yet  prepared  to  decide  whether  oil  is  preferable  on  the  whole  to 
water. 

How  to  illuminate  the  microscope. — In  doing  ordinary 
microscopic  work  it  is  best  to  use  day -light,  such  as  is  reflected 
from  a  clear  sky.  It  is  not  well  to  use  direct  sun-light,  but  to 


10  MANUAL    OF    HISTOLOGY. 

receive  illumination  from  a  point  opposite  to  the  sun.  North 
light  is  very  excellent. 

If  artificial  light  is  to  be  used,  an  ordinary  kerosene  burner 
will  answer  sufficiently  well,  even  better  than  gas.  Some  of 
the  highest  lenses  require  artificial  light. 

Testing  tlie  eye-piece. — Eye-pieces  are  usually  free  from 
serious  defects,  but  if  we  are  desirous  of  testing  one,  the  fol- 
lowing method  may  be  followed  : 

Select  a  combination  of  lens  and  eye-piece  that  gives  a  per- 
fectly flat  field.  Then  remove  the  eye-piece  and  substitute  the 
one  that  is  to  be  tested.  If  now  the  image  is  no  longer  flat, 
the  eye-piece  has  aberration  of  form  and  should  be  rejected. 

Testing  liigh  lenses. — In  combinations  that  magnify  about 
five  hundred  times,  a  good  test  is  the  pleurosigma  angulatum, 
one  of  the  diatoms.  A  lens  that  will  demonstrate  three  sets  of 
lines  by  direct  light  has  a  proper  amount  of  defining  power, 
and  with  the  other  qualifications  already  mentioned,  is  suit- 
able for  the  finer  sorts  of  microscopical  work.  This  task  is 
easily  accomplished  by  either  the  No.  10  immersion  of  Hart- 
nack  or  Prazmowski,  the  TV  of  Wale,  and  also  by  lenses  of  other 
good  makers. 

To  test  the  magnifying  power  of  lenses  even  more  accurately, 
Robert's  test  plates  may  be  used.  They  consist  of  bands  of 
fine  lines  from  nineteen  to  thirty  in  number. 

It  has  usually  been  thought  that  the  eighth  or  ninth  of 
their  series  is  a  good  test ;  the  nineteenth  band,1  however,  has 
been  defined  by  a  ten  immersion  Ilartnack,  and  probably  by  a 
goodly  number  of  American  lenses.  (See  Appendix.) 

Measuring  the  angle  of  a  lens. — Take  an  instrument  of 
which  the  pillar  is  hinged,  and  which  also  revolves  on  its  ver- 
tical axis. 

Measure  off  on  the  table,  in  front  of  the  instrument,  a  semi- 
circle with  the  pillar  as  a  fixed  point.  Divide  the  semicircle 
into  the  proper  number  of  degrees,  viz.,  180. 

Place  opposite  the  instrument,  and  without  the  circle,  a 
candle  or  lamp.  Then  interpose  between  the  two  a  screen  hav- 
ing an  aperture  to  admit  a  small  beam  of  light.  Revolve  the 
tube  on  its  axis  until  the  light  can  no  longer  be  seen  ;  then 


1  According  to  Carpenter,  the  nineteenth  bund  contains  113,595.13580  spaces  to 
the  inch. 


TESTING    THE    MICEOSCOPE ITS    USES.  11 

count  off  the  number  of  degrees  which  the  instrument  has 
passed  over.  Suppose,  that,  in  a  given  case,  the  number  be 
seventy  ;  then  revolve  the  instrument  in  the  opposite  direction 
and  count  as  before.  The  number  of  degrees  will  of  course  be 
the  same. 

Add  the  two  figures  together,  and  the  total  number  of  de- 
grees (viz.,  140)  will  represent  the  angle  of  aperture. 


CHAPTEK  II. 

METHODS  FOB  PKEPABING  MICKOSCOPIC   OBJECTS. 

General  directions. — Microscopic  work  should  be  done  at  a 
rather  low  table,  not  more  than  thirty  inches  high,  and  resting 
squarely  upon  the  floor,  so  that  it  cannot  be  jarred  by  move- 
ments in  the  room.  In  most  laboratories  small  and  short  mi- 
croscopes are  preferred  ;  they  are  now  made  by  nearly  every 
optician.  The  total  height,  when  the  stand  is  vertical,  need 
not  be  more  than  eleven  or  twelve  inches.  For  various  reasons, 
which  soon  become  apparent  to  those  who  do  much  histological 
work,  it  is  seldom  necessary  to  provide  the  stand  with  a  hinge- 
joint,  which  allows  the  tube  to  be  inclined  toward  the  observer. 
A  vertical  and  rigid  stand  is  steadier,  less  expensive,  and,  ex- 
cept in  very  rare  instances,  all  that  is  required  in  medical  work. 

When  the  microscopist  is  about  to  commence  his  examina- 
tion, he  should  select  the  various  materials  that  are  likely  to 
be  needed,  and  place  them  near  him  on  the  table,  so  as  to  be 
within  easy  reach  of  his  hand.  Special  tables  for  microscopic 
work  may  be  provided  with  rows  of  drawers  upon  either  side 
of  the  worker.  In  them  should  be  kept  all  the  microscopic 
accessories  that  he  expects  to  use,  such  as  glass  slides  and 
covers,  wooden  boxes  for  specimens,  labels,  a  note-book  for 
rough  sketches  and  annotations,  a  bit  of  chamois  skin  for 
cleaning  the  lenses  and  other  adjuvants  which  are  found  useful. 
By  so  doing,  these  materials  are  kept  free  from  dust,  and  stand 
ready  for  use  at  any  time.  A  small  vessel  holding  clean  water 
to  wash  the  covers  and  slides,  a  receptacle  of  some  kind  for 
the  waste,  and  a  clean,  fine,  and  soft  towel  should  not  be  for- 
gotten, as  they  are  always  useful  for  every  kind  of  microscopic 
work. 

The  instrument  is  best  kept  under  a  bell-glass  on  the  table. 
If,  however,  it  has  to  be  taken  about  from  place  to  place,  it 


METHODS    FOR    PREPARING    MICROSCOPIC    OBJECTS.  13 

should  be  packed  in  its  box,  and  the  accessories  may  also  be 
kept  in  a  suitable  chest,  such  as  has  been  described,  and  which 
is  made  by  a  number  of  opticians. 

After  the  directions  that  have  been  given,  it  seems  hardly 
necessary  to  add  that  everything  pertaining  to  the  work  should 
be  carefully  cleansed  after  using,  and  put  away  in  its  proper 
place,  so  as  to  be  immediately  available  at  any  future  time. 
The  expenditure  of  a  little  time  in  these  details  is  more  than 
counterbalanced  by  the  greater  rapidity  and  effectiveness  of 
subsequent  work. 

How  to  prepare  afresh  microscopic  object  for  rapid  exam- 
ination.— When  practicable,  every  specimen  should  be  studied 
as  early  as  possible  after  removal  from  the  body,  and  this  is 
important  even  if  it  is  to  be  hardened  and  prepared  for  per- 
manent preservation. 

Take  a  clean  slide,  which,  of  course,  should  be  reasonably 
thin  ;  place  it  before  you  upon  a  white  ground  (some  micro - 
scopists  have  a  square  plate  of  marble  set  into  the  table);  mois- 
ten the  slide  with  a  drop  of  some  indifferent  fluid,  such  as 
iodized  serum  or,  perhaps,  a  three-fourths  per  cent,  aqueous 
solution  of  common  salt ;  then  place  in  the  drop  the  fragment 
to  be  examined.  Small  particles  are  more  easily  studied  than 
large  ones.  Usually  the  substance  should  be  spread  out  a 
little  with  needles. 

In  one  or  two  minutes  it  is  ready  for  examination.  By  this 
method  striped  muscular  tissue  may  easily  be  detected  ;  and  it 
also  happens  to  be  a  good  example  because  it  is  very  frequently 
brought  to  microscopists  for  examination.  In  certain  forms  of 
dyspepsia,  especially  in  women,  it  is  common  for  ingested 
meat  to  pass  through  the  alimentary  tract  with  very  little 
change.  Prepared  for  the  microscope  in  this  simple  way  the 
peculiar  markings  of  striped  muscle  may  be  observed  at  once, 
and  even  if  the  meat  has  been  boiled. 

If,  however,,  the  material  to  be  examined  is  opaque,  we  add 
to  the  drop  of  serum  another  of  glycerine  ;  the  latter  alone  re- 
fracts the  light  too  much,  and  is  therefore  undesirable.  When, 
however,  it  is  combined  with  an  equal  amount  of  serum  or  the 
salt  solution,  the  fluid  has  a  proper  refractive  power  for  most 
histological  purposes.  The  microscopist  should  now  let  fall 
upon  the  drop  a  cover  glass,  and  place  the  slide  upon  the  stage 
of  the  microscope.  Nothing  is  required  to  keep  the  cover  in 


14  MANUAL    OF    HISTOLOGY. 

place.  Examine  at  first  with  a  low  power,  and  then  with  a 
higher  one,  until  the  specimen  has  been  studied  in  all  its 
details. 


THE   ORDINARY  METHODS   OF   PREPARING  TISSUES. 

Mullef  s  fluid. — It  is  customary  to  use  Muller's  fluid  to 
render  tissues  firm,  so  that  they  may  be  easily  cut  with  the 
knife,  and  made  thin  enough  for  microscopic  studies.  The  for- 
mula is  (by  weight)  bichromate  of  potassium,  2  parts,  sulphate 
of  soda,  1  part,  distilled  water,  100  parts.  This  fluid,  which 
is  of  a  brown  color  and  transparent,  is  admirably  adapted  for 
hardening  and  preserving  permanently  nearly  all  the  tissues  of 
the  body  ;  though  for  the  brain  and  cord  it  is  unsatisfactory 
without  the  subsequent  use  of  other  reagents.  It  is,  however, 
very  cheap,  and  specimens  may  be  preserved  in  it  for  years, 
and  still  retain  the  characteristics  which  make  them  suitable 
for  microscopic  study. 

Potassium  bichromate  solution. — Some  microscopists  prefer 
simply  a  solution  of  the  bichromate  of  potassium  (gr.  xv.  —  5  ]•)• 
It  is  well,  in  this  case,  to  put  the  specimens  into  a  fresh  solution 
every  day  for  several  days.  Subsequently  they  are  to  be  hard- 
ened in  alcohol.  The  strength  of  the  latter  should  at  first  be 
eighty  per  cent.,  then  ninety  per  cent.,  and  finally  may  be 
ninety-five  per  cent.  The  alcoholic  process  requires  a  few  ad- 
ditional days.  Solutions  containing  chromic  acid  or  the  bi- 
chromates are  objectionable  if  the  specimen  is  to  be  used  for 
coarse  demonstration,  because  the  yellow  or  brown  color  of  the 
acids  is  difficult  to  remove.  Prolonged  soaking  in  distilled 
water  will  accomplish  a  great  deal,  but  the  final  color  is  gener- 
ally a  clay  brown.  Of  course  this  objection  does  not  apply  to 
microscopic  sections,  and  indeed  it  appears  as  if  the  chromic 
acid  and  chromate  solutions  prepare  them  particularly  well  for 
the  process  of  staining  in  various  colors. 

Ammonia  bichromate  solution. — Gerlach  has  recommended 
this  reagent  in  one  or  two  per  cent,  solutions  for  hardening  the 
brain  and  cord.  It  is  to  be  used  as  the  preceding  (Frey). 

Alcohol  and  acetic  acid  mixture  (Lockhart  Clarke). — Two 
objects  were  sought  by  their  combination :  one  to  coagulate 
albuminous  matters  by  the  alcohol,  the  other  to  render  them 
transparent.  The  proportion  was  alcohol  three  parts  and 


THE    ORDINARY    METHODS    OF    PREPARING    TISSUES.  15 

acetic  acid  one  part.     It  is  said  that  by  this  method  sections  of 
the  cord  may  be  made  transparent  in  a  few  hours  (Frey). 

Alcohol  and  acetic  acid  mixture  (Moleschott). — This  "  strong 
acetic  acid  mixture,"  of  which  the  formula  is  strong  acetic  acid 
(1.070  sp.  gr.),  1  vol.;  alcohol  (.815  sp.  gr.),  1  vol.;  distilled 
water,  2  vols.,  causes  the  connective- tissue  substances  to  be- 
come very  transparent.  Delicate  textures  do  not  tolerate  it 
well  (Frey). 

Molybdate  of  ammonia  has  been  recommended  by  Krause 
for  hardening  specimens.  It  has  met  with  some  favor. 

Solution  of  osmic  and  cJiromic  acids. — Flesch  recommends 
a  union  of  these  acids  for  hardening  and  decalcifying  bone. 
It  is  also  useful  for  hardening  other  tissues.  His  formula  is 
as  follows  :  osmic  acid,  10  parts ;  chromic  acid,  25  ;  aq.  destill., 
100. 

Alcoliol  and  acetic  acid  and  muriatic  acid  solution. — 
Beale  gives  the  following  formula:  water,  1  oz. ;  glycerine,  1 
oz. ;  spirit,  2  oz. ;  acetic  acid,  2  drachms ;  hydrochloric  acid, 
£  drachm.  This  is  said  to  harden  well  and  be  suited  for  epithe- 
lial structures  (Frey). 

Method  of  hardening  the  brain. — Hamilton  recommends 
the  following  method :  pieces  of  brain  and  cord  cut  into  sec- 
tions not  more  than  an  inch  in  length,  or  length  and  breadth, 
are  immersed  in  a  fluid  containing  three  parts  of  Muller'  s  fluid 
and  one  of  methyl  alcohol,  and  put  away  for  some  three  weeks 
in  a  refrigerator.  Then  they  are  to  be  soaked  in  a  solution  of 
the  bichromate  of  ammonia  (1-400)  for  a  week  ;  another  week 
in  a  solution  of  1-100  ;  a  third  week  in  a  solution  of  1  to  50 ; 
and  finally  kept  in  chloral  hydrate  (12  gr.  to  the  ounce).  Be- 
fore cutting,  they  are  to  be  washed  twelve  hours  or  more  in 
water ;  they  then  are  to  stand  forty-eight  hours  in  a  syrup 
containing  two  parts  of  refined  sugar  to  one  of  water.  He  then 
cuts  with  Rutherford's  microtome.  Staining  is  done  with 
osmic  acid  and  carmine. 

For  clarification  he  uses  oil  of  cloves  or  turpentine. 

How  to  embed  specimens. — When  a  piece  of  tissue  is  so 
small  that  it  cannot  be  held  in  the  hand,  it  is  customary  to 
embed  it  in  some  substance  of  about  the  same  consistence.  A 
combination  of  wax  and  oil  answers  the  purpose  very  well ; 
they  should  be  mixed  in  about  equal  proportions  in  a  porce- 
lain dish,  and  then  heated  together  until  the  wax  is  thoroughly 


16  MANUAL    OF    HISTOLOGY. 

melted.  This  having  been  done,  a  mould  should  be  at  hand  to 
receive  both  the  embedding  mixture  and  the  piece  of  tissue. 
Various  moulds  are  in  use.  Some  are  made  of  tin-foil,  and  are 
shaped  like  a  common  earthenware  garden-pot. 

A  fine,  long  cambric  needle  should  be  passed  through  the  tis- 
sue, and  then  (the  mould  being  placed  in  position)  the  point  of  the 
needle  is  to  be  pushed  through  the  bottom  into  the  table  beneath. 

Then  the  mixture  of  the  liquid  wax  and  oil,  which  has  been 
heated  to  the  point  of  melting  and  no  more,  should  be  poured 
slowly  into  the  mould,  so  as  to  slightly  cover  the  specimen. 
During  the  process  of  hardening,  minute  bubbles  of  air  will  be 
liberated  from  the  tissue  ;  they  will  escape  more  rapidly,  and 
the  embedding  material  will  harden  more  quickly  and  thor- 
oughly, if  the  microscopist  blows  gently  and  continuously  on 
the  surface  of  the  liquid.  Just  at  the  moment  when  the  mass 
is  no  longer  liquid,  the  needle  should  be  suddenly  withdrawn. 

As  soon  as  it  is  hard  throughout,  the  tin-foil  mould  may  be 
torn  off  by  breaking  the  edge  at  any  point  with  the  finger. 
The  foil  tears  like  paper. 

When  moulds  are  not  at  hand,  an  excellent  substitute  may 
be  made  with  ordinary  writing  paper.  Some  confectioners 
make  them  of  pressed  paper. 

Embedding  in  glycerine  and  tragacantJi. — Mr.  John  Ste- 
venson's plan  is  as  follows:  He  takes  two  drachms  of  glyce- 
rine and  mixes  them  with  one  drachm  and  a  half  of  powdered 
gum  tragacanth.  The  tissue  to  be  cut  is  then  placed  in  a  small 
pill-box,  and  the  mixture  poured  in.  The  box  is  then  laid 
away  in  a  cool  place  from  eight  to  twelve  hours,  when  sections 
may  be  made  with  the  knife.  In  case  the  specimen  is  to  be 
preserved  for  a  longer  time,  the  bottom  of  the  box  may  be 
taken  off,  and  the  side  slit  up.  The  specimen  will  now  be 
found  embedded  in  a  solid  elastic  cake,  and  may  be  slipped 
into  alcohol  until  required.  When  it  is  to  be  kept  in  spirits 
less  than  twenty-eight  hours,  the  mixture  should  be  glycerine, 
2  drachms  ;  powdered  tragacanth,  1  drachm ;  gum  arabic,  15 
grains.  Tissues  that  have  lain  in  spirit  should  be  steeped  in 
cold  water  a  few  hours  before  embedding. 

The  hand  section-cutter  is  used  by  some  microscopists.  It 
is  simply  a  cylinder  which  is  designed  to  receive  the  object 
and  the  material  in  which  it  is  embedded.  A  plunger,  which 
is  driven  up  from  beneath  by  the  revolution  of  a  screw,  pushes 


THE    ORDINARY    METHODS    OF    PREPARING    TISSUES.          17 

up  the  specimen  so  that  it  may  be  sliced  off  by  an  ordinary 
knife.     For  some  purposes  it  is  very  useful. 

Freezing  section- cutters. —Of  these  there  are  many  in  use, 
and  they  have  certain  advantages.  In  conjunction  with  Dr. 
J.  H.  Hunt,  of  Brooklyn,  I  have  devised  a  modification  of  the 
ordinary  instrument.1  (Fig.  9.) 


FIG.  9. — Freezing  section-cutter :  B,  metallic  box ;  S,  cylinder;  a,  well;  c,  c,  frame  for  holding  knife 
A,  A ;  G,  indicator ;  D,  milled  head ;  F,  F,  plugs ;  E,  E,  tubes  to  fit  in  well ;  H,  H,  covers  to  metallic 
box ;  K,  binding  screw  attaching  box  to  table. 

It  consists  of  the  brass  cylinder,  S,  made  of  rather  large 
size,  and  placed  in  the  centre  of  a  metallic  box,  B.  The 
length  of  the  cylinder,  with  driver,  D,  is  about  five  inches.  The 
diameter  of  the  well,  a,  measures  If  inch.  Fitted  round  and 
about  the  cylinder  is  a  plate  of  glass  which  from  its  smooth- 
ness permits  the  knife  to  sweep  it  easily. 

The  knife,  A,  A,  is  large,  measuring  13  inches  in  length,  in- 
cluding handle  ;  in  breadth,  If  inch.  It  is  fitted  into  a  brass 
frame,  c,  c,  7J  inches  in  length  and  3i  in  breadth.  Two  strong 
brass  springs,  and  two  sliding  clamps,  hold  it  in  place.  The 
knife  is  slightly  concave  on  both  sides. 

The  well  is  so  large  that  it  will  hold  an  ordinary  kidney 
after  hardening,  or  at  least  so  much  of  it  that  a  transverse  sec- 

1  Made  by  Miller  Bros.,  1213  Broadway,  New  York  city. 
2 


18  MANUAL    OF    HISTOLOGY. 

tion  may  be  made  of  the  whole  organ  at  one  sweep  of  the  knife. 
The  knife  and  frame  are  modifications  of  those  devised  by  Dr.  E. 
Curtis  of  this  city,  and  the  section-cutter  and  box  are  not  dif- 
ferent in  any  essential  particulars  from  those  in  common  use. 

They  are  larger,  however,  and  the  indicator,  Gr,  enables  the 
observer  to  determine  with  accuracy  the  thickness  of  his  sec- 
tions. Thus,  in  my  own  instrument  thirty-one  turns  of  the 
milled  head  drives  the  plug  forward  one  inch. 

Each  revolution  consequently  drives  the  specimen  forward 
^T  inch.  Now,  the  circumference  of  the  milled  head  is  marked 
off  into  thirty  divisions. 

When  the  indicator  marks  that  the  plug  has  been  driven 
forward  one  division,  the  distance  traversed  will  be  -§fa  inch. 

It  is  easy,  therefore,  to  determine  the  thickness  of  any  sec- 
tion with  considerable  accuracy. 

When  it  is  desirable  to  put  the  instrument  in  use,  the 
plug  that  is  to  be  used  is  well  oiled,  as  also  the  thread  of  the 
driver,  and  the  metallic  box  is  filled  with  a  mixture  of  ice  and 
snow. 

It  is  necessary  to  be  particular  and  oil  the  bearings 
thoroughly,  else  they  will  bind  and  the  instrument  will  be 
clogged  while  the  freezing  process  is  going  on.  The  usual 
plan  is  to  soak  the  tissue  (as  Dr.  Pritchard  suggests)  in  a 
thick  solution  of  gum,  which  cuts  like  cheese  when  frozen. 
The  soaking  should  continue  for  a  number  of  hours,  say  until 
the  next  day. 

When  the  tissue  is  ready,  a  thick  solution  of  the  guru 
should  be  poured  into  the  well  and  the  tissue  held  until  it  is 
fixed  by  the  ice.  Some  non-conductor  is  to  be  placed  over 
the  well  as  soon  as  fixation  has  commenced,  in  order  that  ac- 
cess of  heat  may  be  prevented. 

If  ice  is  used  it  should  be  ground  up  finely  and  then  packed 
tightly  about  the  well ;  snow  is  better.  The  whole  process 
takes  only  ten  or  fifteen  minutes.  The  freezing  section-cutter 
is  of  use  when  we  are  desirous  of  making  a  rapid  examination 
of  fresh  tissues. 

It  is  obvious  that  they  are  seen  under  more  natural  circum- 
stances than  when  they  have  passed  through  the  bichromate 
or  chromic  acid  solutions,  or  alcohol,  all  of  which  cause  more 
or  less  change  in  such  delicate  substances. 

It  has  been  hoped  that  by  the  freezing  method  we  should 


THE    ORDINARY    METHODS    OF    PREPARING    TISSUES.          19 

learn  much  that  is  new  about  the  finer  structures  of  the  brain 
and  the  character  of  the  corpuscular  elements  of  the  body,  bub 
as  yet  it  has  not  reached  our  expectations. 

Hailes' s  microtome. — A  very  ingenious  and  excellent  instru- 
ment (Fig.  10)  has  been  devised  by  Dr.  William  Hailes,  Pro- 
fessor of  Histology  and  Pathological  Anatomy  at  the  Albany 
Medical  College.  Objections  to  it  will  be  mainly  on  the  ground 
of  price. 

Dr.  Hailes  uses  it  as  a  simple  instrument  or  as  a  freez- 
ing microtome,  arranged  either  for  ice  and  salt,  ether-spray, 
rhigoline,  etc. 

The  employment  of  ice  and  salt  (coarse)  is  preferred,  be- 
cause it  costs  but  little  and  freezes  the  mass  solidly  and 
quickly,  and,  if  desired,  500  or  1,000  sections  can  be  obtained 
in  a  few  moments,  depending,  of  course,  upon  the  rapidity 
and  skill  of  the  operator. 

The  time  of  freezing  is  about  seven  minutes,  except  in 
very  warm  weather,  when  it  requires  a  few  moments  longer. 

The  instrument  does  not  work  quite  so  satisfactorily  in  very 
warm  weather,  owing  to  the  rapid  melting  at  the  surface  of  the 
preparation. 

It  is  absolutely  necessary  that  the  mass  should  be  frozen 
solid,  or  the  sections  cannot  be  cut  smoothly. 

An  extra  freezer  may  be  employed,  and  while  one  specimen 
is  being  cut  the  other  is  being  frozen  ;  by  exchanging  cylinders 
(they  being  interchangeable)  no  delay  is-  necessary. 

The  art  of  cutting  is  readily  acquired.  Two  hundred  or 
two  hundred  and  fift}^  sections  have  been  made  in  a  minute, 
and  of  a  uniform  thickness  of  TYVo-  °f  an  inch.  It  is  not 
necessary  to  remove  the  sections  from  the  knife  each  time, 
but  twenty  or  thirty  may  be  permitted  to  collect  upon  the 
blade.  They  lie  curled  or  folded  up  upon  the  knife,  and  when 
placed  in  water,  straighten  themselves  out  perfectly  in  the 
course  of  a  few  hours.  The  knife  employed  is  an  ordinary 
long  knife  from  an  amputating  case. 

Perfectly  fresh  tissues  may  be  cut  without  any  previous 
preparation,  using  ordinary  mucilage  (acacia)  to  freeze  in,  but 
most  specimens  require  special  preparation. 

If  preserved  in  Miiller's  fluid,  alcohol,  etc.,  they  require  to 
be  washed  thoroughly  for  several  hours,  and  then,  according 
to  the  suggestion  of  Dr.  David  J.  Hamilton,  F.R.C.S.,  etc.,  of 


20 


MANUAL    OF    HISTOLOGY. 


the  University  of  Edinburgh,  Scotland,  the  specimen  is  placed  in 
a  strong  syrup  (sugar,  two  ounces  ;  water,  one  ounce)  for  twenty- 
four  hours ;  it  is  then  removed  to  ordinary  mucilage  for  forty- 
eight  hours,  and  finally  is  cut  in  the  freezing  microtome. 

These  sections  may  be  kept  indefinitely  in  a  preservative 


FIG.  10. 


FIG.  10.— Poly-microtome  (without  freezing  apparatus) :  A,  small  well  fitting  on  pyramidal  bed-plate ; 
B,  pyramidal  bed-plate  containing  different  sizes;  C,  micrometer  screw;  D,  ratchet-wheel  attached  to 
screw ;  E,  lever  actuating  the  micrometer  screw  by  means  of  a  pawl  engaging  in  teeth  of  ratchet-wheel ; 
F,  arm  carrying  a  dog,  which  prevents  back  motion  of  screw  ;  G,  regulator  for  limiting  the  throw  of 
lever,  and  consequently  governing  the  micrometer  screw  ;  H,  lever-nut  for  fixing  regulator  ;  I,  index,  with 
pointer  and  graduated  scale,  from  1/2400  inch  to  1/200  inch  ;  K,  knife  for  cutting  sections ;  L,  knob  to 
turn  micrometer  screw  direct  when  pawls  are  detached ;  M,  table  clamp ;  T,  table  of  microtome,  with 
glass  top  to  facilitate  cutting. 

FIG.  11.— (Very  much  reduced  in  size).  A,  B,  tube  containing  specimen  which  is  surrounded  by  freez- 
ing mixture  in  tin  receiver  C,  D ;  B,  F,  revolving  hopper  with  wings,  W,  W,  for  stirring  the  ice ;  G,  out- 
let for  melted  ice. 


fluid  recommended  by  Dr.  Hamilton: 
destil.,  aa.  f  iv.  ;  acid,  carbolic.,  gtt.  iij. 
addition  of  alcohol,  §  ij.,  is  advisable. 


$.    Glycerin.,  aquae 
Boil  and  filter.     The 


STAINING    FLUIDS.  21 

TJie  Vincent  microtome. — This  instrument,  which  was  de- 
vised by  Dr.  Vincent,  of  New  York  city,  is  a  flat  piece  of  steel 
(Fig.  12)  12  inches  long  by  2— 2£  inches  wide,  with  a  bevelled 
cutting  edge,  6  inches  long.  The  handle  is  simply  the  rounded 
and  smoothed  extremity  of  the  knife. 

It  has  been  in  use  at  the  School  of  Histology  connected  with 
the  Columbia  Veterinary  College,  and  has  proved  to  be  a  very 
efficient  knife. 

The  mode  of  action  is  very  simple.  The  object  having  been 
previously  placed  in  any  ordinary  hand-cylinder  and  mounted 


in  wax,  paraffine,  or  pith,  the  sections  are  made  by  a  stroke  of 
the  knife,  which  is  pushed  straight  forward.  As  will  be  readily 
seen,  the  larger  the  section  the  wider  the  knife  must  be. 

The  blade  is  made  of  the  best  plate  steel,  and  is  easily  kept 
in  order. 


STAINING  FLUIDS. 

Ammonia  carmine. — This  is  one  of  the  oldest  and  best 
known  solutions.  Take  one  part,  by  weight,  of  the  best  car- 
mine, which  is  known  as  "  No.  40,"  dissolve  it  in  100  parts  of 
distilled  water,  and  add  one  part  of  aqua  ammonise.  The  pre- 
vious dull  color  now  gives  place  to  a  most  brilliant  and  deep 
red.  It  is  necessary,  however,  that  the  carmine  be  either  neu- 
tral or  very  faintly  alkaline,  else  the  color  will  diffuse  and  the 
tissues  will  not  be  differentiated.  Expose  the  fluid,  therefore, 
for  some  weeks  to  the  air,  or  evaporate  over  the  water-bath 
until  the  odor  of  ammonia  is  no  longer  perceptible. 

The  nuclei  should  be  deeply  and  brightly  stained,  while  the 
intercellular  substance  is  in  no  way  affected.  •  If,  however, 
diffusion  has  taken  place,  a  great  deal  of  it  may  be  removed 
by  soaking  the  section  in  a  saturated  alcoholic  solution  of  ox- 
alic acid.  When  a  brick-red  color  has  in  this  way  been  ob- 
tained, the  object  has  been  accomplished.  Crystals  of  oxalic 
acid  are  apt  to  be  found  in  specimens  that  have  been  prepared 


22  MANUAL    OF   HISTOLOGY. 

in  this  way.  It  is  therefore  desirable,  after  using  the  acid,  to 
wash  thoroughly  in  alcohol  or  water. 

Borax  carmine  (Arnold's  formula). — The  following  method 
is  given  by  Dr.  M.  N.  Miller  as  the  one  in  use  by  students  in 
the  histological  laboratory  of  the  New  York  University.  It 
originated  with  Prof.  J.  W.  S.  Arnold.  A  saturated  solution 
of  borax  is  prepared  in  a  wide-mouthed  pint  bottle.  The  borax 
should  be  in  some  excess.  "No.  40"  carmine  is  now  added 
to  the  solution  under  constant  agitation,  until  after  a  while  it 
no  longer  dissolves,  and  an  excess  remains  at  the  bottom  of  the 
vial,  mingled  with  the  crystals  of  borax.  After  twenty-four 
hours  the  supernatant  fluid  is  decanted.  To  this  clear  portion 
f.  ^ij-  of  alcohol  are  added,  and  f.  3  j.  of  caustic  soda  solution 
(U.  S.  P.).  The  staining  solution  is  now  ready.  Or,  the  alco- 
hol may  be  omitted  (Arnold),  and  the  liquid  evaporated  to  dry- 
ness  ;  the  red  amorphous  mass  is  then  powdered.  Of  this, 
15  grains  are  placed  in  an  ounce  of  water,  to  which  f.  3  j.  of 
alcohol  is  added.1 

Sections,  after  staining,  should  be  washed  in  alcohol  to  re- 
move the  superfluous  coloring  fluid,  and  then  transferred  to  a 
saturated  solution  of  oxalic  acid  in  alcohol  to  fix  the  color. 
The  oxalic  acid  is  then  washed  out  in  alcohol ;  finally  the  sec- 
tions are  cleared  up  in  oil  of  cloves,  and  mounted  in  balsam  or 
dammar. 

Double  staining  by  borax  carmine  and  indigo  carmine. — 
Drs.  W.  T.  Norris  and  E.  O.  Shakespeare,  of  Philadelphia, 
have  recommended  a  method  which  is  a  modification  of  Mer- 
kel's.  Two  staining  fluids  are  made,  one  red  and  the  other 
blue.  The  red  one  contains  carmine,  gr.  7J ;  borax,  3  ss. ;  dis- 
tilled water,  1  j.  The  blue  contains  indigo  carmine,  3  ss. ;  bo- 
rax, 3  ss. ;  and  distilled  water,  3  vij. 

After  thorough  trituration  the  ingredients  are  mixed  and 
left  in  a  vessel ;  the  supernatant  fluid  is  then  poured  off.  The 
sections,  if  previously  hardened  in  bichromate,  picric  acid,  or 
chromic  acid,  should  be  well  washed  ;  they  then  are  to  be 
placed  for  a  few  minutes  in  a  mixture  (equal  parts)  of  the  red 
and  blue  fluids,  then  transferred,  without  washing,  to  a  satura- 
ted solution  of  oxalic  acid  and  allowed  to  remain  in  it  rather 
less  time  than  in  the  staining  fluid.  When  sufficiently  bleached 

1  [This  preparation  of  borax  carmine  is  the  best  that  I  have  ever  used. — T.  E.  S.] 


STAINING    FLUIDS.  23 

the  sections  should  be  washed  in  water  until  every  trace  of  ox- 
alic acid  is  removed.  .Sections  thus  prepared  may  be  mounted 
in  balsam  or  dammar.  Connective- tissue  substances  are  blue, 
while  the  nuclei  are  red.  The  osseous  lamellae  of  bone  are 
blue,  the  cells  in  the  lacunae  red,  while  the  marrow  is  apple- 
green. 

Picro-carmine  (Miller's).— Add  one  part  of  a  saturated  so- 
lution of  picric  acid  to  two  parts  of  the  15-graih  borax  carmine 
solution  (Arnold's).  The  epithelium  of  the  glands  and  the 
muscles  are  stained  yellow,  while  the  nuclei  of  the  cells  and  the 
connective  tissues  acquire  the  carmine  color.  Sections  should 
remain  in  the  picro-carmine  solution  for  about  twenty -four 
hours.  Next  they  are  washed  quickly  in  water,  then  in  alcohol, 
after  which  they  are  transferred  to  the  oil  of  cloves.  (For  Ran- 
vier's  method  of  making  picro-carmine,  see  the  chapter  upon 
the  Histology  of  the  Nervous  System.) 

Hcematoxylin  solution  (Boehmer' s). — Dissolve  20  grains  of 
hsematoxylin  in  one-half  an  ounce  of  absolute  alcohol ;  then 
dissolve  2  grains  of  alum  in  an  ounce  of  water.  Some  drops  of 
the  first  solution  are  added  to  the  second,  which,  after  a  short 
time,  becomes  a  beautiful  violet.  It  improves  after  keeping  for 
a  few  days,  and  should  always  be  filtered  before  using  (Thin). 

Hcematoxylin  solution  (Kleinenburg' s). — First  make  a  satu- 
rated solution  of  the  chloride  of  lime  in  seventy  per  cent,  alco- 
hol, and  add  alum  to  saturation. 

Then  make  a  saturated  solution  of  alum  in  seventy  per 
cent,  alcohol.  Add  the  first  to  the  second  in  the  proportion  of 
one  to  eight.  To  the  mixture  add  a  few  drops  of  a  saturated 
solution  of  hsematoxylin  in  absolute  alcohol  (Thin). 

Hcematoxylin  solution  (Miller's  method). — Take  a  pint  bot- 
tle, as  in  the  former  process,  fill  with  water,  and  add  about  an 
ounce  of  common  extract  of  logwood  in  coarse  powder.  Allow 
this  to  remain  in  a  warm  place  for  twenty -four  hours,  with 
occasional  stirring.  After  the  expiration  of  this  time  add  pow- 
dered commercial  alum  until  the  liquid  changes  from  the 
muddy  brown  color  given  by  the  logwood  to  a  brilliant  purple. 

The  alum  is  to  be  added  until  no  change  is  produced.  An 
excess  of  the  salt  will  do  no  harm.  Add  about  f.  I  j.  of  alcohol, 
and  after  decanting  or  filtering  it  is  ready  for  use.  One 
may  omit  the  alcohol  at  this  stage,  and  evaporate  to  dryness 
as  in  the  borax-carmine  process.  The  powder  thus  obtained  is 


24  MANUAL    OF    HISTOLOGY. 

added  to  water  when  required.  Three  grains  to  the  ounce  of 
water  will  give  a  fluid  that  will  stain  alcohol-hardened  tissue 
in  from  ten  to  fifteen  minutes.  A  solution  containing  ten 
grains  to  the  ounce  will  stain  very  quickly.  If  it  is  desired  to 
keep  the  solution,  add  f.  §  j.  of  alcohol  for  each  ounce.  Hsema- 
toxylin  stainings  are  soaked  in  water  for  a  few  minutes  to 
wash  out  the  alum,  then  transferred  to  alcohol,  clarified  in  the 
clove  oil,  and  finally  mounted  in  balsam  or  dammar. 

Klein }s  formula  for  Ticematoxylin. — Mix  in  a  mortar  5 
grammes  of  the  officinal  extract  of  hsematoxylin,  with  15 
grammes  of  alum,  and  pulverize  carefully.  To  this  add  grad- 
ually 25  c.c.  of  distilled  water,  and  filter.  To  the  residue  add 
15  c.c.  of  distilled  water  and  again  mix  in  a  mortar,  and  filter ; 
to  this  filtrate  add  2  grammes  of  alcohol.  Now  mix  the  two 
filtrates  and  keep  in  a  glass-stoppered  bottle.  If  the  liquid 
should  at  any  time  become  muddy,  filter  again.  Care  must  be 
taken  to  prevent  any  acid  from  intermingling  with  the  fluid. 
Acids  cause  the  hsematoxylin  to  turn  red  ;  for  this  reason,  sec- 
tions which  have  been  hardened  in  chromic  acid  should  be 
placed  in  a  watch-glass  and  covered  with  distilled  water,  to 
which  add  a  drop  or  two  of  a  30  per  cent,  solution  of  caustic 
potassa  ;  allow  it  to  remain  therein  10  to  15  minutes.  To  use 
the  hsematoxylin  fluid,  add  a  few  drops  to  an  ounce  of  distilled 
water,  so  as  to  make  a  pale  violet  solution  ;  allow  sections  to 
remain  in  this  solution  for  12  to  24  hours.  Or,  a  stronger  so- 
lution may  be  employed  which  will  stain  specimens  in  10  to  30 
minutes,  and  still  give  good  results.  Mount  in  glycerine,  ace- 
tate of  potassa,  balsam,  or  better,  resinous  turpentine. 

Eosine  solution. — Eosine,  first  introduced  by  Fischer  in 
1875,  is  much  used  in  staining  fresh  preparations.  It  is  cus- 
tomary to  have  a  strong  solution  of  one  to  ten  or  twenty  on 
hand.  A  few  drops  are  then  added  to  a  watch-glassful  of  water 
or  alcohol.  Fresh  tissues  are  both  stained  and  hardened.  It 
affects  the  body  of  the  cells,  together  with  the  nuclei.  It  is  apt 
to  diffuse,  unless  special  care  is  taken,  and  long  soaking,  say 
for  twenty-four  hours,  is  practised. 

Double- staining  with  cosine  and  other  aniline  colors. — 
Schiefferdecker  first  stains  in  an  alcoholic  solution  of  eosine 
and  then  in  a  one  per  cent,  watery  solution  of  an  aniline  color 
(dahlia,  methyl  violet,  or  aniline  green).  Care  must  be  taken 
not  to  extract  the  color  when  dehydrating  the  specimen  in 


STAINING    FLUIDS.  25 

alcohol  according  to  the  usual  method  ;  very  deep  staining  is 
therefore  desirable. 

Green  coloration  of  the  nuclei. — To  effect  this,  Tafani  em- 
ploys a  fluid  containing  three  or  four  parts  of  a  saturated 
watery  solution  of  aniline  blue  to  some  six  or  seven  parts  of  a 
saturated  watery  solution  of  picric  acid. 

Eosine  and  Jicematoxylinfor  staining  bone. — Busch  recom- 
mends eosine  and  hsematoxylin  for  double-staining  the  zone  of 
ossification  in  growing  bone.  The  sections  of  decalcified  bone 
are  first  immersed  a  few  days  in  a  one-half  per  cent,  chromic 
acid  solution,  or  in  a  one  per  cent,  solution  of  the  bichromate 
of  potassium,  and  then,  after  washing  with  water,  in  a  watery 
solution  of  eosine.  In  young  bone,  where  ossification  is  pro- 
gressing, the  cartilage  matrix  is  blue,  while  the  nuclei  of  the 
cartilage-cells  adjoining  the  line  of  bone  are  red ;  the  contents 
of  the  medullary  spaces  are  also  bright  red,  while  in  the  bone 
trabecles  there  is  a  combination  of  blue  and  red. 

Eosine  for  permanent  specimens. — Renaut  has  employed 
eosine  to  differentiate  all  forms  of  protoplasm,  whether  bodies 
or  their  processes.  He  either  employs  a  watery  solution  alone, 
or  with  the  admixture  of  one-third  its  volume  of  alcohol. 
The  coloration  is  obtained  after  immersion  of  the  sections  from 
one-half  minute  to  one  minute.  They  are  then  washed  in 
distilled  water,  and  may  be  preserved  in  a  neutral  solution  of 
glycerine  to  which  one  per  cent,  of  chloride  of  sodium  has  been 
added  to  prevent  the  glycerine  dissolving  the  eosine.  These 
preparations  will  then  remain  unchanged  for  months. 

In  examining  the  fixed  corpuscles  of  the  subcutaneous  tis- 
sue, the  same  author  injects  beneath  the  skin  a  solution  of 
eosine  and  water  (1-500),  and  then  removes  a  portion  of  the  in- 
filtrated tissue  with  the  scissors.  The  fibrous  fascicles  are  un- 
affected, while  the  elastic  fibres  take  the  color  deeply. 

The  fixed  corpuscles  appear  as  red  granular  plates,  while 
their  nuclei  take  a  very  intense  color.  This  reagent,  therefore, 
is  well  suited  for  the  study  of  connective  tissues.  In  special 
instances  the  silver  method  may  be  used  first,  and  then  the 
eosine. 

Preparation  of  tlie  cornea. — Klein  has  adopted  the  follow- 
ing plan  for  exhibiting  this  most  delicate  tissue.  He  first  burns 
the  centre  of  the  cornea  of  a  kitten  with  caustic  potash,  and 
then,  twenty-four  hours  later,  brushes  the  surface  with  nitrate 


26  MANUAL    OF    HISTOLOGY. 

of  silver,  and,  half  an  hour  afterward,  immerses  it  in  water 
acidulated  with  acetic  acid  ;  after  a  day  or  two  it  is  found  to 
have  a  glutinous  appearance.  The  lamellae  are  then  easily 
stripped  off,  and  in  the  middle  portions,  the  corneal  corpuscles 
assume  a  purplish-brown  color  while  their  nuclei  are  uncol- 
ored.  The  outlines  of  the  lymphatic  channels  are  also  sharply 
defined . 

Picro-hcematoxylin  and  eosine  (triple-staining). — Wendt 
has  described  a  method  of  double-staining  by  picric  acid  and 
hsematoxylin.  Only  the  very  thinnest  sections,  however,  give 
satisfactory  results.  A  strong  solution  of  hsematoxylin  is  first 
employed.  In  this  the  sections  are  allowed  to  remain  about 
twelve  hours.  After  washing  them  in  water,  they  are  placed 
in  a  saturated  solution  of  picric  acid  and  carefully  watched. 
They  may  be  removed  from  time  to  time,  examined  with  a  low 
power,  and,  when  properly  stained,  put  in  alcohol  and  mount- 
ed in  Canada  balsam  with  as  little  delay  as  possible.  To  ob- 
tain triple- staining,  eosine  may  be  conveniently  combined  with 
this  picro-hsematoxylin  method.  To  insure  good  results  some 
amount  of  practice  is  necessary. 

Double,  triple,  and  quadruple  staining. — Dr.  Gibbes  re- 
commends for  double-staining,  immersion  first  in  picro-carmine 
and  then  in  logwood,  or  which  is  better,  immersion  first  in  a 
spirituous  solution  of  rosine  or  aniline  violet,  and  then  in  an 
aqueous  solution  of  aniline  blue  or  iodine  green.  In  obtaining 
more  than  two  colors  there  is  considerable  difficulty.  To  ac- 
complish it  he  uses  first  the  chloride  of  gold  or  picro-carmine 
and  then  the  spirituous  and  aqueous  solutions  of  the  ani- 
lines. 

Staining  with  BismarJc  brown.— Make  a  watery  solution  of 
gr.  ij. —  3J-,  heat  and  filter;  soak  in  the  solution  about  three 
minutes ;  set  the  color  with  acetic  acid  (glacial)  4  per  cent, 
for  half  a  minute.  After  dehydrating  with  alcohol  mount  in 
dammar  varnish.  Weigert  prepares  the  Bismark  brown  as 
follows  :  he  makes  a  concentrated  aqueous  solution  by  boil- 
ing in  water,  filtering  from  time  to  time.  He  also  uses  a  weak 
alcoholic  solution,  and  combines  with  other  colors. 

[To  combine  with  eosine — put  the  sections  in  a  strong  aqueous  solution  of 
Bismark  brown ;  remove  after  about  two  minutes,  set  in  weak  acetic  acid  (four 
per  cent.),  then  place  in  a  weak  alcoholic  or  aqueous  solution  of  eosine,  and 
then  again  in  the  acetic  acid  solution. — T.  E.  S.] 


STAINING   FLUIDS.  27 

Solution  of  alum-carmine.— Grenadier  recommends  this 
fluid :  Take  a  one  to  five  per  cent,  solution  of  ordinary  alum, 
or  ammonia  alum  ;  boil  with  one-half  to  one  per  cent,  powdered 
carmine  for  twenty  minutes.  Filter,  and  add  a  little  carbolic 
acid  to  preserve. 

Naphthaline  yellow  for  bone. — In  sections  of  the  femur 
from  a  foetal  pig,  three  and  a  half  inches  in  length,  the  follow- 
ing method  was  found  to  yield  very  excellent  results  : 

After  immersion  for  three  days  in  Miiller's  fluid,  sections 
were  made,  and,  after  washing  in  water,  immediately  dipped  in 
an  alcoholic  solution  of  naphthaline  yellow  (gr.  iv. —  J  j.) ;  after 
eight  to  ten  minutes  the  sections  were  removed,  and  dipped  in 
a  watery  solution  of  acetic  acid  of  three  per  cent. ;  then  they 
were  immersed  for  about  ten  minutes  in  the  ordinary  solution 
of  ammonia-carmine,  rendered  neutral  by  exposure  to  the 
air. 

The  sections  were  again  dipped  in  the  acetic  acid  solution 
in  order  to  set  the  color,  and  then  placed  in  alcohol  of  eighty 
per  cent.,  and  subsequently  in  absolute  alcohol. 

The  specimens  thus  stained  showed  a  matrix  of  deep  trans- 
parent chrome  yellow.  The  young  bone-corpuscles  and  osteo- 
blasts,  on  the  other  hand,  together  with  the  fibrous  tissue, 
assumed  a  brilliant  rose  color,  thus  affording  an  excellent  con- 
trast between  forming  and  formed  bone. 

Staining  with  methyl-green  and  induline. — Calberla  has 
introduced  two  new  substances  into  use,  viz.,  methyl-green  and 
induline.  The  one  stains  the  nuclei  of  the  cells  of  the  sub- 
cutaneous tissue,  the  nuclei  of  vessels  and  nerve-sheaths  rose 
color,  while  the  cells  of  the  corium  and  their  nuclei  are  a 
violet  red ;  the  other  colors  the  cells  of  the  Malpighian  layer 
a  greenish  blue.  Combinations  of  methyl  green  and  eosine  are 
also  recommended.  Eosirie  (one  part)  and  methyl  green  (sixty 
parts)  are  to  be  dissolved  in  a  thirty  per  cent,  solution  of  warm 
alcohol.  The  epithelial  nuclei  take  a  violet  blue,  the  nuclei 
of  connective  tissue  a  greenish  blue,  and  the  cell-body  a  red 
color.  Singular  differentiations  are  made ;  thus,  while  the 
striated  muscle  is  red,  the  nuclei  are  green.  On  the  other 
hand,  smooth  muscular  tissue  is  green,  and  the  intercellular 
substance  red.  In  the  salivary  glands  the  cells  of  the  excretory 
ducts  are  blue,  while  the  so-called  secretory  cells  are  red.  In- 
duline dissolves  in  warm  water  and  in  dilute  alcohol.  Take  a 


28  MANUAL    OF    HISTOLOGY. 

concentrated  watery  solution,  dilute  it  with  six  times  its 
volume  of  water,  then  immerse  the  preparations  from  5  to  20 
minutes,  wash  them  out  and  clarify  in  oil  of  cloves  or  glycerine. 
The  peculiarity  of  this  material  is  that  it  never  affects  the 
nucleus,  but  only  the  cell-body.  More  frequently,  however,  it 
is  the  intercellular  substance  that  is  colored  blue. 

Purpurine. — Ranvier  has  recommended  this  dye,  which  is 
extracted  from  madder.  Alum  (one  part)  is  dissolved  in  dis- 
tilled water  (two  hundred  parts) ;  the  fluid  is  then  heated  to 
the  boiling  point  in  a  porcelain  dish.  Thea  a  small  quantity 
of  purpurine  is  dissolved  in  distilled  water  and  added  to  it. 
Sufficient  purpurine  should  be  added  to  leave  a  residue,  by 
which  it  is  certain  that  the  solution  is  saturated.  While  still 
hot  it  is  to  be  filtered  into  alcohol  of  one-fourth  the  total 
volume.  The  fluid  has  an  orange  red  color,  and  is  more  effi- 
cient when  fresh.  Sections  should  be  immersed  from  24  to  48 
hours. 

Frencli  arcJiil — Staining  with  extract. — Wedl  uses  this 
substance,  which,  after  the  loss  of  the  ammonia,  is  dissolved 
in  20  c.c.  absolute  alcohol,  5  c.c.  acetic  acid  of  1.070  sp.  gr., 
and40c.c.  of  distilled  water  so  as  to  make  a  saturated  solu- 
tion. Protoplasm  and  matrix,  but  not  nuclei,  are  colored  a 
beautiful  red. 

Alizarine. — This  aniline  color  is  recommended  by  Than- 
hoffer,  but  experience  is  limited  with  reference  to  it.  It  has  a 
golden  yellow  color,  and  is  easily  fixed  by  the  tissues. 


METALLIC   SOLUTIONS. 

Staining  with  osmic  and  oxalic  acids. — Broesicke  adopts 
the  following  method : 

Little  pieces  of  fresh  or  freshly  dried  preparations  are  left 
for  an  hour  in  a  one  per  cent,  solution  of  osmic  acid ;  then 
they  are  carefully  washed  and  soaked  in  a  cold  saturated  solu- 
tion of  oxalic  acid,  and  finally  examined  in  water  or  gly- 
cerine. Elastic  fibres  are  yellow,  fat  is  black,  while  the  walls 
of  capillaries  and  many  connective- tissue  substances  are 
red. 

Chloride  of  gold  and  lemon  juice.  —  Ranvier  is  in  the 
habit  of  demonstrating  the  corneal  nerves  by  using  lemon- 


METALLIC    SOLUTIONS.  29 

juice  in  which  the  tissue  is  left  five  minutes.  Then  it  is  soaked 
for  15  to  20  minutes  in  3  c.c.  of  a  one  per  cent,  solution  of  the 
gold  chloride,  and  finally  25  to  30  minutes  in  distilled  water 
to  which  one  or  two  drops  of  acetic  acid  has  been  added.  After 
two  or  three  days'  exposure  to  the  sun,  the  fibres  become  dis- 
tinct. 

Nitrate  of  silver  in  solution  (gr.  j. — iv. —  §  j.)  is  much  used. 
The  details  of  the  method  will  be  found  in  the  Chapter  on  the 
Lymphatics. 

Chloride  of  gold  has  also  been  much  used  in  studying 
the  so-called  lymph-canalicular  system  of  the  cornea.  The 
method  of  employing  it  will  be  found  in  the  section  relating  to 
the  cornea. 

Osmic  acid  in  solution  is  also  very  useful.  Its  effects  are 
given  in  the  chapter  on  the  General  Histology  of  the  Nervous 
System. 

Methyl-green  for  showing  waxy  change. — Curschmann,  of 
Hamburg,  has  recommended  this  reagent  to  effect  the  same 
object  as  the  molet  de  Paris  of  Cornil.  A  solution  of  about 
five  grains  to  the  ounce  is  used.  The  specimens  are  bathed  in 
the  fluid  a  few  minutes  or  hours.  They  take  the  color  quickly. 
After  staining  they  may  be  mounted  in  glycerine.  The  amy- 
loid material  assumes  a  brilliant  rose  color.  The  surrounding 
tissue  takes  a  dull  green. 

Wicliersheimer's  preserving  liquid.  — This  material  has 
been  extensively  used  of  late,  and  there  are  several  formulae 
for  it.  Among  the  most  recent  modifications  is  that  made  by 
the  firm  of  Poetz  &  Flohr,  of  Berlin.  For  immersing  speci- 
mens the  ingredients  are :  arsenious  acid,  12  grains ;  sodium 
chloride,  60  grains  ;  potassium  sulphate,  150  grains  ;  potassium 
nitrate,  18  grains;  potassium  carbonate,  15  grains;  water,  10 
litres  ;  glycerine,  4  litres  ;  wood  naphtha,  i  litre.  A  modified 
fluid  is  used  for  injecting  the  blood-vessels.  This  is  suitable  for 
all  fresh  tissues,  preserving  them  in  their  natural  color  and 
consistence. 

If  the  tissues  are  to  be  used  subsequently  for  the  micro- 
scope, it  is  said  that  they  should  be  washed  thoroughly  in 
water,  but  it  seems  from  recent  experiments  that  the  fluid  un- 
fits them  for  minute  examination.  It  is  also  rather  expensive, 
and  has  an  extremely  pungent  and  unpleasant  odor. 


30  MANUAL    OF    HISTOLOGY. 


METHODS   OF   INJECTING   THE  BLOOD-VESSELS.1 

Good  injections  are  hard  to  make,  requiring  skill,  patience, 
and  practice.  First  of  all,  it  is  essential  to  have  a  perfectly 
transparent  injecting  material.  This  is  usually  made  up  with 
gelatine  and  colored  by  carmine  or  Prussian  blue.  When 
carmine  is  used  it  is  customary  to  dissolve  it  in  ammonia,  fil- 
ter, and  then  add  it  to  the  solution  of  gelatine.  In  order  to 
obtain  a  neutral  or  faintly  acid  liquid,  acetic  acid  is  added, 
drop  by  drop,  until  the  alkalinity  is  overcome,  but  there  must, 
at  the  same  time,  be  no  precipitation  of  carmine,  which  is  best 
detected  by  the  granules  of  carmine  seen  in  the  field  of  the 
microscope.  If  alkaline,  the  color  diffuses  and  the  result  is 
a  failure. 

It  is  difficult  to  lay  down  any  rule  in  reference  to  the  amount 
of  acetic  acid  necessary ;  the  color  of  the  liquid  is  the  best 
and  only  satisfactory  test.  The  ammoniacal  odor,  if  very 
slight,  cannot  be  detected,  and  therefore  is  useless  as  a  test. 
A  slight  excess  of  acid,  however,  will  do  no  harm. 

The  preparation  of  the  blue  injecting  fluid  is  less  difficult. 

Usually  Brucke's  soluble  Berlin  blue  is  used;  it  can  be 
procured  at  most  of  the  large  drug  stores,  but  if  not  obtaina- 
ble, may  be  made  as  follows  (Klein) : 

"  Take  of  potassic  ferrocyanide  217  grammes,  and  dissolve  in 
one  litre  of  water  (solution  A).  Take  one  litre  of  a  ten  per  cent, 
solution  of  ferric  chloride  (solution  B).  Take  four  litres  of  a 
saturated  solution  of  sulphate  of  soda  (solution  C).  Add  to 
A  and  B  two  litres  of  C.  Then,  with  constant  stirring,  pour 
the  ferric  chloride  mixture  into  a  vessel,  collect  the  precipitate 
upon  a  flannel  strainer,  returning  any  blue  fluid  which  at  first 
escapes  through  the  pores  of  the  flannel ;  allow  the  solutions 
to  drain  off.  Pour  a  little  distilled  water  over  the  blue  mass, 
returning  the  first  washing  if  colored,  and  renew  the  water 
from  day  to  day  until  it  drips  through  permanently  of  a  deep 
blue  color.  This  is  a  sign  that  the  salts  are  washed  away,  and 
all  that  is  further  necessary  is  to  collect  the  pasty  mass  from 
the  strainer  and  allow  it  to  dry." 

Having  obtained  the  soluble  Berlin  blue,  it  will  be  much 

1  Prepared  for  the  editor  by  Dr.  W.  H.  Porter,  Curator  of  the  Presbyterian  Hos- 
pital, New  York  city. 


METHODS    OF   INJECTING    THE   BLOOD-VESSELS.  31 

simpler  to  inject  both  arteries  and  veins  with  the  same  solution. 
If  a  small  animal  is  to  be  employed  (as  the  rabbit,  for  instance) 
it  will  be  found  most  convenient  to  inject  through  the  aorta. 
If,  however,  an  organ  from  the  human  body  is  to  be  injected, 
through  the  main  vessels  of  that  part.  To  commence  with,  the 
kidney  is  probably  the  best,  as  it  is  small  and  of  firm  consis- 
tence. 

For  injecting  with  the  red  gelatine  liquid  the  following  rules 
will  be  found  of  service,  and  yield  good  results : 

Take  40  grammes  of  Cox's  best  English  gelatine,  place  it 
in  a  jar,  and  add  just  water  enough  to  cover  it ;  let  it  stand 
for  several  hours,  when  it  will  imbibe  the  water,  being  hygro- 
scopic ;  it  may  then  be  dissolved  over  a  water-bath. 

Take  of  the  carmine  22  grammes  and  dissolve  in  40  c.c.  of 
aqua  ammonite,  then  add  240  c.c.  distilled  water,  and  filter. 
The  preparation  of  the  carmine  solution  had  better  be  com- 
menced the  day  before,  as  it  takes  about  twenty-four  hours  to 
filter.  The  gelatine  and  carmine  solutions  are  raised,  separately, 
to  the  same  temperature,  when  the  gelatine  solution  is  gradu- 
ally added  to  the  carmine  solution,  under  constant  stirring. 
The  injection  fluid,  which  is  now  of  -a  deep  cherry-red  color  and 
alkaline  reaction,  is  precipitated  with  acetic  acid  until  the  deep 
cherry  color  gives  place  to  a  bright  red,  and  the  ammoniacal 
odor  is  exchanged  for  that  of  acetic  acid.  At  this  point  a  little 
more  acid  may  be  added  without  doing  harm.  In  case  the 
liquid  should  be  found  too  concentrated,  a  little  more  water 
may  be  added.  For  the  blue  mass  the  following  method  may 
be  adopted : 

Take  66  grammes  of  gelatine,  and  prepare  as  in  the  former 
case.  Add  4  grammes  of  soluble  Berlin  blue  in  substance  and 
360  c.c.  of  water. 

The  blue  will  also  be  found  slow  in  filtering.  When  both 
are  heated  to  the  same  temperature  add  the  gelatine  to  the 
blue  solution,  with  constant  stirring.  When  this  has  been 
done,  a  solution  of  the  iron  salts  may  be  added  to  intensify  the 
blue  color,  care  being  exercised  not  to  add  enough  of  the  iron 
to  coagulate  the  gelatine.  This  liquid  also  may  be  diluted 
if  found  so  concentrated  that  it  will  not  flow  easily.  The 
liquids  having  been  prepared,  the  organ  carefully  removed 
from  the  body,  thoroughly  washed  out  and  heated  to  a  tem- 
perature of  98°  F.,  everything  is  ready  for  injection.  The  fill- 


32  MANUAL    OF    HISTOLOGY. 

ing  of  the  vessels  may  be  accomplished  in  one  of  two  ways : 
either  by  forcing  in  the  fluid  with  a  syringe  or  by  the  pressure 
of  a  column  of  water.  The  syringe  is  the  simplest,  but  requires 
practice  and  skill  in  manipulation. 

Having  inserted  the  canula  into  the  artery,  the  kidney  may 
be  entirely  filled  with  either  the  red  or  blue  injecting  liquid. 
When  the  organ  is  seen  to  be  swollen,  tense,  and  well  colored 
the  vessels  must  be  tied  off,  and  the  kidney  placed  in  a  freez- 
ing mixture  until  the  gelatine  has  set.  When  this  is  accom- 
plished, the  organ  should  be  cut  into  small  pieces,  and  placed 
first  in  a  weak  solution  of  alcohol  (seventy  per  cent,  or  less), 
and  the  strength  of  the  alcohol  gradually  increased  until  the 
specimen  is  sufficiently  hard  for  cutting.  The  object  of  using 
weak  alcohol  is  to  prevent  too  great  shrinkage  of  the  gelatine. 
If  two  colors  are  used,  it  is  impossible  to  tell  beforehand  how 
much  fluid  will  be  necessary  to  fill  the  arterial  arid  venous  sys- 
tems, and  not  have  the  one  encroach  on  the  other.  For  an 
ordinary  kidney,  about  250  c.c.  of  the  injecting  liquid  should 
be  prepared  to  fill  the  arterial  vessels,  and  nearly  double  to 
fill  the  veins.  The  following  rules  must  be  observed  in  inject- 
ing :  keep  the  gelatine  solutions  and  the  organ  as  nearly  as 
possible  at  the  same  temperature.  Immerse  the  organ  in  warm 
water  during  the  process.  Avoid  the  entrance  of  air  into  the 
canula  when  connecting  the  syringe.  Inject  slowly,  and  give 
the  fluid  time  to  work  its  way  into  the  minute  capillary  rami- 
fications. 

The  above  rules  can  be  applied  to  any  organ,  with  such 
modifications  as  will  suggest  themselves  to  the  operator. 


BIBLIOGRAPHY. 

KLEIN.     Handbook  of  the  Physiological  Laboratory.     Edited  by  Sanderson.    Vol.  I. 

1873. 

BDSCH.     Arch.  f.  Mikroskop.  Anat.     XIV.     1877. 

NORRIS  and  SHAKESPEARE.    American  Journal  of  the  Medical  Sciences,  Oct.,  1877. 
KENAUT.     Archives  de  physiol.     2me  Se'rie,  T.  IV.     1877. 
SCIIAEFER.     Histology  and  the  Microscope.     Philadelphia,  1877. 
THIN.     Practical  Histology.     London,  1877. 
WENDT.     Ueber  die  Hardersche  Druse,  etc.     Strassburg,  1877. 
KANVIER.     Traite  technique  d'histologie.     Paris,  1877-8. 
BROESICKE,  J.    Med.  Centralblatt.  46.     1878. 


BIBLIOGRAPHY.  33 

CALBERLA.     Morpholog.  Jahrb.     III.     H.  &  S.'s  Jahrb.    I.     1878. 

HAMILTON.     Journal  of  Anatomy  and  Physiology.     Vol.  XII.     1878. 

MILLER.     New  York  Medical  Record,  Feb.  2,  1878,  p.  97. 

RANVIER.     Journ.  de  micrograpbie.     H.  &  S.'s  Jahrb.     1878. 

SCIIIEFPERDECKER.     Arch.  f.  mikrosk.  Anat.     XIV.     1878. 

TAFANI.     Journal  de  micrographie.     1878. 

WEDL.     Virchow's  Arcbiv,  74.     1878. 

WEIGERT.    Arch.  f.  mikrosk.  Anat.     XV.,  p.  259.     1878. 

FLESCH.     Archiv  f .  mikrosk.  Anat.     XVI.,  p.  300.     1879. 

GRENACHER.     Arch.  f.  mikrosk.  Anat.     XVI.,  p.  463.     1879. 

KLEIN  and  E.  NOBLE  SMITH.     Atlas  of  Histology.     1879-80. 

CDRSCHMANN.     Archiv  f.  Path.  Anat.     LXXIX.,  III.     1880. 

FREY.     The  Microscope  and  Microscopical  Technology.     New  York,  1880. 

GIBBES.     Lancet,  March  20,  1880. 

HAILES.     An  Improved  Microtome.     New  York  Medical  Record,  July  24,  1880. 

THANHOFFER,  L.  v.     Das  Mikroskop  u.  seine  Anwendung.     Stuttgart,  1880. 

VINCENT.     New  York  Medical  Record,  June  12,  1880. 

WICKERSHEIMER.     Arch.  f.  Pharm.     New  Remedies,  May,  1880. 

GIBBES.     Practical  Histology  and  Pathology.     Philadelphia,  1881. 

SEILER.     Compendium  of  Microscopical  Technology.     Philadelphia,  1881. 

STOWELL.     The  Student's  Manual  of  Histology.     Detroit,  1881. 

HARRIS  and  POWER.     Manual  for  the  Physiological  Laboratory.     New  York,  1881. 

3 


CHAPTER    III. 

THE  BLOOD. 

IN  man  and  most  vertebrates  the  blood  consists  of  a  clear 
fluid,  the  liquor  sanguinis  or  plasma,  in  which  a  large  num- 
ber of  corpuscles  are  very  evenly  distributed.  Of  these  there 
are  two  prominent  varieties,  differing  much  in  character — the 
red  and  the  colorless  or  white.  The  former  are  greatly  in  ex- 
cess, and  give  to  the  liquid  its  characteristic  red  appearance. 

In  relative  proportion  the  two  vary  greatly  within  certain 
limits.  Usually  there  is  but  one  of  the  white  to  600  or  1,200  of 
the  red  ;  but  these  numerical  relations  are  disturbed  by  vari- 
ous diseases,  and  the  white  may  equal  the  red,  or  even,  in  rare 
cases,  exceed  them. 

In  fresh  liquid  blood  the  corpuscles  are  the  only  solid  mat- 
ters visible  under  the  microscope ;  nor  is  there  any  difference 
in  this  respect  with  coagulated  blood,  when  the  quantity  is 
large.  If,  however,  a  little  should  be  allowed  to  dry,  fibrin 
may  be  deposited  under  the  form  of  delicate  filaments,  which 
are  superimposed  on  one  another  without  definite  order. 

In  one  hundred  volumes  of  blood  there  are  said  to  be  thirty- 
six  volumes  of  corpuscles  and  sixty-four  of  plasma.  This  ratio, 
however,  is  altered  somewhat  by  different  conditions,  such  as 
the  age  and  health  of  the  individual. 

The  red  corpuscles  in  man  and  other  mammals,  with  very 
few  exceptions,  are  bi-concave  bodies,  circular  in  outline.  In 
birds,  amphibia,  and  almost  all  fishes  they  are  also  bi-concave 
or  hollowed  out  at  the  centre,  but  have  an  elliptical  contour. 
In  the  human  species  nuclei  or  central  bodies  appear  at  a  very 
early  period  of  life,  but  subsequently  are  invisible,  unless  arti- 
ficial means  are  used  to  display  them.  In  birds,  amphibia,  and 
fishes  a  rounded  prominence  is  also  seen  at  the  centre,  which  is 
particularly  well  marked  when  the  corpuscle  happens  to  be 


THE    BLOOD. 


35 


turned  so  that  its  edge  meets  the  eye.  This  prominence  cor- 
responds to  the  ordinary  nucleus  of  other  elementary  bodies  or 
cells.  In  this  position  the  peculiar  shape  of  the  corpuscles, 
with  their  constricted  centres  and  rounded  extremities,  has 
suggested  a  comparison  between  them  and  the  little  cakes 
known  as  lady's-fingers.  (See  Fig.  13.) 

It  is  obvious  also  that  this  varying  thickness  of  the  disk  will 
have  some  effect  upon  the  microscopic  image,  for  the  whole 
superficies  cannot  be  in  focus  at  one  time,  even  when  the  cor- 


FIG.  13.— Red   corpuscles  of 
the  frog.     (Rollett.) 


FIG.  14. — Human  red  blood-corpuscles :  a,  globules 
showing  the  double  contour;  6,  globules  turned  on 
edge  ;  c,  the  same  in  rouleaux  like  coin.  (Rollett.) 


puscle  is  turned  flatwise  to  the  eye.  There  will  be  some  differ- 
ence between  the  level  of  the  thickest  and  thinnest  portions. 
As  a  result,  when  one  is  dark  the  other  is  bright,  when  one  is 
well  defined  the  other  is  blurred.  This  statement  serves  for  an 
explanation  of  the  double  contour  that  is  sometimes  observed 
in  human  blood  (see  Fig.  14),  though  it  has  also  been  offered 
in  support  of  the  theory  that  the  semi-solid  and  elastic  matter 
of  which  the  disk  is  mainly  composed  has  an  external  envelope 
or  limiting  membrane  of  different  density.  It  is  to  be  remem- 
bered, however,  that  the  property  of  double  refraction  which 
explains  the  double  contour,  belongs  to  all  transparent  bodies 
that  have  rounded  edges,  such  as  drops  of  water  or  oil,  in 
which  cases  there  is  plainly  no  enveloping  or  peripheral  wall. 
When  the  lens  and  eye-piece  are  suitably  combined,  as  in  the 
best  microscopes,  the  double  marking  is  often  difficult  or  im- 
possible to  discover.  On  the  other  hand  a  poor  optical  com- 
bination will  generally  exhibit  it  to  an  unpleasant  degree,  and 


36  MANUAL    OF    HISTOLOGY. 

especially  if  great  amplification  is  aimed  at.  Lenses  of  very 
high  power  are  also  apt  in  any  case  to  exhibit  the  same  ap- 
pearances. 

Measurements  of  the  red  corpuscles  in  man  and  ani- 
mals.— The  average  diameter  of  the  human  red  globule  is  still 
a  matter  of  discussion.  The  faulty  measurements  of  the  older 
writers  have  led  to  some  misconception  on  these  points,  and  the 
matter  has  required  new  study.  Welcker,  who  has  long  been 
an  authority  on  the  Continent,  gave  .00774  mm.  as  the  average 
breadth  in  the  human  male,  with  a  minimum  of  .0045  mm.,  the 
latter  from  personal  observation.  A  maximum  of  .010  mm. 
has  been  given  by  Max  Schultze,  while  Frey  places  the  average 
thickness  at  .0018  mm.  Later  investigations  by  Hayem  show 
that  a  diameter  of  .012  mm.  or  even  .014  mm.  may  be  reached, 
while  he  has  known  it  to  fall  as  low  as  .0022  mm.  Elsberg 
gives  the  mean  diameter  of  the  red  blood-corpuscle  at  .0075 
mm.,  agreeing  very  nearly  with  Welcker.  He  has  observed  a 
maximum  of  .01016  mm.,  and  a  minimum  of  .00422  mm. 

Measurements  of  single  corpuscles  have  no  value  in  deter- 
mining the  particular  animal  from  which  the  blood  has  been 
obtained,  and  this  is  an  object  of  prime  importance  in  medico- 
legal  cases.  It  is  common,  therefore,  to  make  a  hundred  or 
more  single  measurements,  and  then  take  the  average  of  them. 
And  yet  this  figure  may  vary  considerably  in  different  individ- 
uals, or  even  in  the  same  one.  In  the  blood  of  the  puppy,  for 
instance  (the  size  of  the  dog's  corpuscle  being  very  nearly 
that  of  man's),  a  recent  observer  found  that  the  average  diame- 
ter of  fifty  corpuscles  varied  only  two-millionth  of  an  inch 
from  a  like  average  of  fifty  taken  from  his  own  blood.  In 
another  instance,  taking  forty  from  a  puppy,  he  found  that 
the  average  differed  onty  seven-millionth  of  an  inch  from  a 
similar  average  of  his  own  (Woodward). 

Opposite  is  given  a  table  of  blood-corpuscle  measurements 
by  Welcker  and  others. 

By  referring  to  it,  the  cat's  and  rabbit's  corpuscles  will  be 
found  to  have  an  average  diameter  which  is  not  far  distant 
from  man's  and  dog's,  while  the  minimum  and  maximum 
diameters  of  each  show  conclusively  that  a  large  number  of 
their  corpuscles  would  be  likely  to  equal  man's,  and  there- 
fore make  it  impossible  to  distinguish  one  from  the  other.  To 
obviate  this  source  of  error  a  very  large  number  of  corpuscles 


THE    BLOOD. 


37 


would  have  to  be  measured  separately,  as  we  have  already 
seen,  and  then  an  average  taken  of  them  all,  before  even  a 
guarded  opinion  could  be  given  as  to  the  source  of  the  blood. 
Still  other  difficulties,  however,  are  apt  to  beset  the  microscop- 
ist.  The  blood  is  usually  dried  and  in  small  quantity.  The 
disks  are  then  shrunken.  If  we  endeavor  to  restore  them  to 
their  original  shape,  as  by  soaking  in  blood-serum,  we  are 
never  sure  of  having  accomplished  the  object,  or  that  we  have 
not  overdone  it.  This  statement  will  be  better  understood  by 
experiments  that  will  be  detailed  at  another  point  in  this 
chapter.  Where  blood-corpuscles  are  elliptical,  as  in  birds, 
there  is  much  less  opportunity  for  error. 


Measurements  of  red  Blood-corpuscles. 


Maximum 
diameter. 

Minimtrm 
diameter. 

Average 
diameter. 

Dog1 

mm. 

.0082 

mm. 
.0065 

mm. 

.0073 

Cat     

.0074 

.0058 

.0065 

Rabbit  

.0080 

.0062 

.0069 

Sheep 

0056 

0038 

0050 

Goat  (old)           .  .            

0046 

.0036 

.0041 

"     (eight  days  old)  

.0066 

.0039 

.0054 

Moschus  javanicus  

.0030 

.0022 

.0025 

Elephant  

.0106 

.0084 

.0094 

Pigeon  (old)                 ...            ... 

0160 

.0132 

.0147 

k  '      (fledfflinff) 

.0140 

.0116 

.0126 

Chicken  ...           

.0132 

.0104 

.0121 

Duck                     

.0140 

.0118 

.0129 

.0066 

.0054 

.0061 

Triton  cristntus           -                      . 

.0327 

.0259 

.0293 

Salamandra  Cryptobranchus               

.0415 

.0302 

.0378 

Japonicus                          

.0579 

.0400 

.0512 

.0440 

.0360 

.0410 

Average 
length. 

Average 
breadth. 

mm. 

.058 

mm. 

.034 

Amphiuna  tridactylum  (Schmidt)    

.075 

.047 

The  number  of  the  red  globules.— It  has  commonly  been  held 
that  the  blood  of  an  adult  man  contains  5,000,000  red  corpus- 
cles in  each  cubic  millimetre.  In  anaemic  conditions  this  num- 
ber may  be  reduced  below  3,000,000,  while  in  fair  physical 


38  MANUAL    OF    HISTOLOGY. 

health  it  has  reached  6,000,000  and  over.  Under  ordinary  cir- 
cumstances 4,500,000  is  thought  to  argue  a  fair  bodily  condi- 
tion (Keyes). 

Quite  recently  Hayem  has  given  an  instance  where  the  number  was  reduced 
to  800,000.  This  extraordinary  state  he  has  called  agkibulie  intense;  the  name 
aglobulie  extreme  was  given  to  a  condition  observed  on  another  occasion  where 
he  counted  only  450,000  corpuscles. 

The  l>lood-globules  in  an  indifferent  fluid. — In  order  to  get 
a  proper  conception  of  the  various  influences  that  act  upon  the 
red  corpuscles,  so  as  to  alter  their  form,  size,  and  internal 
appearance,  it  is  essential  to  subject  them  to  some  of  the  more 
common,  such  as  water,  acids,  alkalies,  electricity,  etc.  In 
no  other  way  can  the  student  appreciate  the  extraordinary 
changes' which  these  bodies  suffer,  and  indeed  a  knowledge  of 
such  matters  is  quite  necessary  in  studying  the  histology  of 
either  normal  or  diseased  tissues. 

Unfortunately  we  are  not  always  able  to  use  human  blood 
for  these  demonstrations  because  the  corpuscles  are  too  small, 
and  consequently  the  alterations  do  not  admit  of  easy  observa- 
tion. We  naturally  turn  to  an  object  that  has  larger  corpuscles 
and  may  be  procured  with  little  trouble  or  expense. 

The  frog  is  therefore  selected,  or,  even  better  still,  the  newt, 
which  is  especially  well  suited  for  this  purpose.  At  first  the 
blood  may  be  examined  in  a  menstruum  similar  to  the  liquor 
sanguinis  or  plasma,  and  the  frog's  aqueous  humor  is  usually 
found  satisfactory. 

To  a  drop  of  this  latter  add  an  equal  quantity  of  the  blood, 
mix  them  well  with  a  glass  rod,  and  adjust  an  ordinary 
|  inch  circle.  The  aqueous  humor  exerts  no  special  influ- 
ence over  the  corpuscles,  and  is  therefore  called  an  indif- 
ferent fluid.  If  it  be  impossible  to  obtain  aqueous  humor,  an 
excellent  substitute  may  be  found  in  the  fresh  fluid  from  a 
hydrocele  or  ovarian  cyst,  or  we  may  use  serum  to  which  iodine 
has  been  added,  which  is  then  called  iodized  serum.  To  six 
ounces  of  the  fluid  twenty  grains  of  finely  powdered  iodine  are 
added.  After  prolonged  agitation  the  iodine  will  be  dissolved, 
and  the  mixture  thus  prepared  may  be  kept  for  a  number  of 
months.  Suspended  in  this  liquid  the  blood  is  studied  to 
advantage  with  a  lens  of  moderate  power,  such  as  an  ordinary 


THE    BLOOD.  39 

i  inch.  The  contents  of  the  disk  will  appear  homogeneous, 
which  is  a  term  that  merely  indicates  an  apparent  absence  of 
structure.  The  nucleus  and  nucleolus  should  also  be  invisible. 
The  shape  of  the  corpuscles  is  oval,  and  they  are  flattened  and 
have  rounded  edges,  with  hollowed  centres,  in  which  a  promi- 
nence is  usually  seen  (Fig.  13).  The  protoplasm  is  the  sub- 
stance of  which  the  disk  is  made  ;  it  has  a  light  yellow  color, 
and  is  dull  or  pellucid  in  appearance,  much  like  semi-solid 
jelly. 

Brownian  and  amoeboid  movements.  —  Using  the  same 
method  of  preparation  the  white  corpuscles  or  leucocytes  are 
seen  to  good  advantage.  They  are  much  smaller  than  the  red 
disks  (in  the  frog — the  reverse  of  human  blood),  and  there  is 
wide  range  in  size,  one  histologist  (Klein)  having  described  as 
many  as  thirty  varieties.  In  the  interior,  little  dark  spots  are 
sometimes  seen  in  constant  vibration.  By  a  skilled  observer  they 
are  readily  detected,  even  with  a  good  \  inch  glass.  When 
such  specks  are  numerous  the  bodies  are  said  to  be  granular. 
In  the  newt's  blood  this  phenomenon  is  usually  best  seen. 
The  word  granule  has  been ,  applied  in  these  cases  from  the 
notion  once  prevalent  that  the  little  dots  were  molecules  sus- 
pended in  a  menstruum  of  some  sort  that  filled  the  corpuscle. 
This  subject  is  now  eliciting  much  study,  but  the  movement, 
whatever  its  significance  may  be,  is  called  the  Brownian  move- 
ment. 

Klein,  who  states  that  the  newt's  leucocyte  is  traversed  by  an  intracellular 
network,  believes  that  the  movement  just  described  is  due  to  the  motion  of  the 
"disintegrated  network"  under  the  stimulus  of  imbibed  water.  Under  this 
explanation  the  oscillatory  movement  in  the  corpuscles  of  the  human  saliva 
would  indicate  death  rather  than  life.  When  fluid  has  been  withdrawn  by 
evaporation  the  phenomenon  ceases.  According  to  other  histologists  this 
vibratile  motion  is  an  indication  of  vital  action. 

The  remarkable  change  in  form  which  these  corpuscles  un- 
dergo is  a  more  positive  indication  of  vital  power  in  the  leuco- 
cyte. When  the  little  body  is  placed  under  conditions  which 
imitate  those  of  its  natural  state  it  commences  to  put  forth 
processes  and  then  withdraw  them,  carrying  on  these  move- 
ments slowly,  but  with  a  certain  degree  of  regularity.  While 
this  is  being  accomplished  the  corpuscle  is  observed  to  move 
about  from  place  to  place. 


40 


MANUAL    OF    HISTOLOGY. 


FIG.  15.— Leucocytes:  a,  putting  out  pro- 
>,  having  withdrawn  them.     (Rollett.) 


In  Fig.  15  the  leucocytes  are  seen.  Those  marked  with  the 
letter  a  are  engaged  in  amoeboid  motion.  The  one  marked  b 
i?  in  a  state  of  contraction.  This  phenomenon  is  called  amoe- 
boid movement,  because  it  resem- 
bles that  of  the  amoeba — the  lit- 
tle microscopic  organism  found 
in  stagnant  water.  In  order  to 
permit  these  changes  to  continue 
for  some  length  of  time,  it  is  well 
to  paint  a  little  oil  or  glycerine 
around  the  edge  of  the  circle. 
Evaporation  is  thus  prevented. 

If  the  warm  slide  be  used  the 
changes  will  follow  with  greater 
rapidity.  Both  Brownian  and 

amoeboid  movements  are  usually  confined  to  a  limited  number 
of  the  corpuscles,  and  the  former  often  to  only  a  small  portion 
of  the  interior. 

The  slide *  for  heating  consists  of  an  ordinary  glass  slide 
(Fig.  16)  upon  which  is  riveted  a  thin  copper  plate  (b)  perfor- 
ated in  the  centre,  so  as  to  allow  space  for  the  drop  of  blood 
which  is  to  be  examined.  From  the  copper  plate  extends  an 
arm  (c)  over  which  is  slipped  a  spiral  copper  wire  (e),  which  is 
heated  by  the  flame  of  an  alcohol  lamp.  By  this  means  the 
glass  plate  is  kept  warm  and  with  it  the  drop  of  blood.  In 
order  to  secure  a  proper 
amount  of  heat  and  no 
more,  it  is  customary 
to  put  a  little  bit  of 
cocoa  butter  upon  the 
corner  of  the  slide.  The 
butter  melts  at  the  tem- 
perature of  the  body, 
and  after  this  point  has 
been  reached  the  lamp 
should  be  carried  along 
the  wire  away  from  the  slide  until  the  precise  distance  is  found 
at  which  this  particular  degree  of  heat  will  be  maintained. 
Action  of  a  dilute  salt  solution. — It  is  often  difficult,  and, 


FIG.  16. — Slide  for  heating  :  o,  slide;  &,  copper  plate ;  c,  arm 
over  which  the  spiral  wire  (d)  is  slipped 


1  Made  by  T.  H.  McAllister,  49  Nassau  Street,  New  York  City. 


THE    BLOOD.  41 

indeed,  impossible,  to  obtain  aqueous  humor  or  even  an  animal 
Huid  such  as  has  been  described,  and  microscopists  have  accord- 
ingly made  use  of  a  substitute  that  can  be  prepared  at  any  time 
and  kept  indefinitely.  This  is  a  solution  of  common  salt  in 
distilled  water  (1 — 400).  Add  a  drop  of  fresh  frog's  blood  to  a 
drop  of  the  salt  solution,  mix  them  well,  and  it  will  be  seen 
that  the  delicate  protoplasm  of  the  red  blood-corpuscle,  most 
susceptible  of  change,  is  not  altered  in  appearance,  though  the 
body  itself  will  change  in  form  from  the  elliptical  to  the  spher- 
ical. This  salt  solution  has  been  found,  in  practice,  an  excellent 
substitute  for  blood-serum,  and  is  very  generally  used  in  ex- 
amining fresh  specimens,  where  it  is  important  to  avoid  any 
material  change  in  the  corpuscle. 

Action  of  distilled  water — Irrigation. — The  effect  of  water 
is  also  noteworthy,  as  it  is  a  very  important  consideration  in 
both  histological  and  pathological  work,  especially  the  latter. 
Take  a  drop  of  frog's  blood,  add  to  it  an  equal  quantity  of 
distilled  water  and  apply  a  cover.  The  nucleus  or  central  body 
will  now  be  readily  seen,  surrounded  by  a  yellow  border  ;  the 
body  of  the  corpuscle  or  peripheral  part  will  at  the  same  time 
gradually  become  paler  and  larger.  Now  add  distilled  water 
slowly,  drop  by  drop,  in  the  following  way  :  Take  a  long  strip 
of  tissue  or  filter  paper  about  half  the  length  of  the  slide  and  in 
breadth  equal  to  one-half  the  diameter  of  the  cover.  Apply 
the  water  with  an  ordinary  minim  dropper,  close  to  the  edge  of 
the  cover,  on  the  side  opposite  to  the  paper  strip.  This  latter 
will  now  take  up  the  excess  of  water  and  cause  a  stream  to 
pass  through  the  specimen.  This  process  is  called  irrigation. 
Push  the  paper  a  short  distance  under  the  edge  of  the  cover, 
and  the  solid  particles  in  the  fluid  will  be  carried  to  the  edge 
of  the  paper,  where  they  will  remain  at  rest  and  may  be  ob- 
served at  one' s  leisure. 

This  plan  is  often  useful  in  other  sorts  of  microscopic  work,  as  in  looking 
for  renal  casts,  urinary  crystals,  etc.  It  may  save  much  valuable  time.  I  first 
learned  it  from  my  friend,  Dr.  Edward  Curtis,  of  this  city. 

Continued  addition  of  water  will  cause  the  corpuscles  to 
swell  and  after  a  time  burst,  or,  at  any  rate,  become  so  expand- 
ed that  they  can  scarcely  be  seen.  When  water  is  applied 
slowly  to  human  blood,  the  corpuscles  soon  begin  to  lose  their 


MANUAL    OF    HISTOLOGY. 


disk-like  form  and  assume  a  spheroidal,  perhaps  spherical  con- 
tour. The  coloring  matter  then  escapes,  in  most  instances,  and 
they  become  quite  transparent  (see  Fig.  17).  Such  corpuscles  are 
often  seen  in  human  urine  where  they  appear  as  colorless  rings. 
In  frog's  or  newt's  blood  the  body  of  the  disk  first  imbibes  the 


FIG.  17. — Human  red  blood-globules : 
a,  with  haemoglobin ;  6,  without  it.    (Rol- 

l3tt.) 


FIG.  18.— Red  corpuscles  of  the  frog 
that  have  imbibed  water.     (Rollett.) 


water ;  later,  the  nucleus,  which  then  has  a  sharply  defined 
outline.  Sometimes  the  material  of  which  the  body  is  largely 
composed  (haemoglobin)  is  gathered  about  the  nucleus,  sending 
off  radiating  prolongations  to  the  periphery,  while  the  imbibed 
fluid  is  stored  in  the  intervening  spaces  (see  Fig.  18). 

Action  of  carbonic  acid  gas. — This  experiment  requires  a 
special  apparatus.  First  of  all  it  is  essential  to  have  a  moist 
chamber  (Fig.  19). 

Take  a  small,  flat  bit  of  wood  about  1J  inch  wide,  3  inches 
long,  and  f  inch  thick ;  make  a  square  opening  in  the  centre, 
sufficiently  large  to  admit  an  ordinary  f  inch  cover-glass  ;  this 
is  to  be  pressed  to  the  bottom  and  firmly  fixed,  thus  making  a 

shallow  well  with  a  glass 
bottom.  Into  this  cham- 
ber are  admitted,  through 
side  holes,  glass  tubes  (one 
on  each  side),  so  that  air 
or  gases  can  be  carried  into  the  chamber.  When  in  use,  the 
chamber  is  kept  moist  by  a  drop  of  water,  which  is  put  in 
one  corner  of  the  well,  while  the  specimen  of  blood  to  be  ex- 
amined is  dropped  upon  a  large  glass  cover,  and  the  latter  in- 
verted over  the  mouth  of  the  well.  In  determining  the  effect 
of  carbonic  acid  gas  upon  animal  life,  we  have  merely  to  con- 
nect the  gas-chamber  just  described  with  a  jar  in  which  carbonic 


FIG.  19.— Moist  chamber. 


THE    BLOOD.  43 

acid  gas  is  generated.  Fig.  19  illustrates  a  gas  or  moist  cham- 
ber of  the  same  general  character,  and  devised  by  Dr.  J.  H. 
Hunt,  of  Brooklyn.  Take  a  large  gallon  flask,  fill  it  partly 
full  of  pulverized  marble-dust,  attach  it  by  means  of  a  rubber 
tube  through  a  perforated  stopper  to  a  Wolff's  bottle,  which 
latter  must  be  connected  with  the  moist  chamber.  Now  gener- 
ate the  carbonic  acid  gas  in  the  flask  by  pouring  muriatic  acid 
upon  the  marble-dust.  When  the  gas  is  being  evolved  it  will 
be  known  by  the  ebullition  of  the  water  in  the  Wolff's  bottle. 
Now  place  the  moist  chamber  upon  the  stage  of  the  micro- 
scope. Take  a  drop  of  newt's  blood,  dilute  it  with  serum  or  an 
indifferent  fluid,  and  mount  it  upon  a  glass  cover,  which  invert 
over  the  well,  first  seeing  that  the  edge  of  the  cover  is  oiled,  so 
that  it  will  remain  in  place.  Now  connect  the  tube  of  the  moist 
chamber  with  the  tube  of  the  gas-generator,  and  the  carbonic 
acid  gas  will  enter  and  pass  through  the  chamber.  The  rapidity 
with  which  the  current  moves  may  be  regulated  by  a  spring 
clip.  As  soon  as  the  gas  enters,  the  central  body  or  nucleus 
becomes  distinctly  visible,  and  is  surrounded  by  a  yellow  halo ; 
when,  however,  the  gas  is  withdrawn  and  atmospheric  air 
is  admitted,  the  nucleus  and  colored  zone  disappear.  This 
double  experiment  may  be  repeated  a  number  of  times.  Finally 
a  point  will  be  reached  where  all  action  will  cease.  This  cen- 
tral body,  under  such  circumstances,  has  been  called  the  zooid, 
and  the  corpuscles  proper  the  oikoid  (Bruecke). 

Action  of  acids  upon  the  blood. — Acetic  acid  is  commonly 
used  in  observing  the  changes  that  are  produced  by  an  acid 
solution. 

Take  the  ordinary  dilute  watery  solution  of  acetic  acid 
(1  per  cent.)  so  much  used  in  laboratories,  add  a  drop  of  it  to 
an  equal  amount  of  frog's  blood.  The  red  globules  instantly 
exhibit  nuclei.  The  colorless  globules  also  cease  their  motion, 
if  any  has  existed,  and  they  become  granular  and  shrivelled. 
The  term  granular  is  used  merely  in  a  relative  sense  and  has  no 
special  reference  to  granules  whether  present  or  not,  but  merely 
to  an  appearance  that  has  already  been  explained. 

These  phenomena  are  more  marked  if  the  solution  is  con- 
centrated. The  red  bodies,  also,  in  such  case,  are  apt  to  crack 
and  split  up.  A  good  way  of  determining  the  proper  strength 
for  the  ordinary  acetic  acid  solution  is  to  pour  a  little  into  an 
ordinary  watch-glass,  and  then  add  chemically  pure  acetic 


44  MANUAL    OF    HISTOLOGY. 

acid  drop  by  drop  until  the  solution  is  faintly  acid  to  the 
taste. 

Action  of  alkalies  upon  the  Hood. — Take  a  drop  of  the 
newt's  blood  and  mount  it  in  a  drop  of  serum  or  of  salt  solu- 
tion. Then,  affixing  a  strip  of  bibulous  paper  in  the  way  that 
has  been  described,  add  drop  by  drop  a  weak  solution  of  aqua 
ammonite.  A  similar  strip  of  paper,  somewhat  larger  in  size, 
upon  the  other  side,  will  cause  a  current  and  carry  the  corpus- 
cles to  the  side  of  the  field  where  the  paper  strip  is  largest,  and 
there  the  corpuscles  may  be  observed  at  rest,  and  the  altera- 
tions effected  by  the  alkali  duly  noted.  It  will  be  seen  that 
after  a  little  time  the  corpuscles,  both  red  and  colorless,  will 
swell  up  and  finally,  after  a  time,  provided  the  alkali  be  in 
sufficient  amount,  disappear  or  become  so  expanded  as  to  be 
invisible.  Sometimes  they  will  burst,  leaving  the  field  evenly 
stained  with  a  homogeneous  glutinous-looking  substance. 

Action  of  electricity. — It  seems  to  make  little  difference,  so 
far  as  the  microscope  is  concerned,  whether  the  continuous  or 
interrupted  current  is  employed,  as  in  either  case  the  phe- 
nomena observed  are  the  same  in  quality.  Take  bits  of  tin- 
foil and  attach  them  to  an  ordinary  glass  slide,  in  such  a 
way  that  they  are  just  -§-  inch  distant  from  one  another.  The 
pieces  of  foil  should  be  triangular  in  shape  and  have  their 
pointed  extremities  turned  to  one  another.  The  specimen 
should  be  a  drop  of  newt's  blood  diluted  with  an  equal  amount 
of  serum,  both  perfectly  fresh.  They  should  be  intimately 
mixed  with  a  glass  rod. 

Depositing  a  drop  of  this  solution  upon  a  cover-glass,  it 
should  be  inverted  and  placed  upon  the  slide  in  such  a  wa}^ 
that  it  occupies  an  intermediate  position  between  the  bits  of 
tin-foil.  The  ordinary  stage  clips  of  the  microscope  are  then 
to  be  used  in  holding  the  slide  firmly  ih  position  and  to  press 
upon  the  tin-foil.  The  only  remaining  task  is  the  attaching  of 
conducting  wires  from  the  electrical  instrument,  one  to  each 
clip.  The  bits  of  tin-foil  are  easily  fastened  to  the  slide  ;  they 
have  merely  to  be  hammered  out  flat,  when  they  will  adhere  by 
simple  pressure.  Sometimes  it  may  be  desirable  to  approxi- 
mate the  poles.  In  such  cases  it  is  necessary  to  use  two  fine 
bits  of  platinum  wire.  They  should  be  flattened,  and  shaped 
like  the  letter  S.  Rest  them  upon  the  bits  of  tin-foil,  opposite 
to  one  another  and  at  the  required  distance  apart.  The  cover- 


THE    BLOOD.  45 

glass  should  press  on  them.  Some  little  mechanical  dexterity 
is  required  to  get  them  in  position,  and  they  are  apt,  after  using, 
to  become  so  charged  that  their  action  upon  the  corpuscles 
commences  before  they  are  connected  with  the  battery.  The 
phenomena  at  the  negative  pole  are  those  of  an  acid ;  at  the 
positive,  those  of  an  alkali.  At  a  distance  from  the  line  of  the 
current,  secondary  changes  occur  of  a  less  regular  character. 

Harting  has  devised  an  apparatus  which  is  somewhat  more 
elaborate,  but  in  principle  the  same. 

Other  changes  in  the  red  corpuscles. — If  a  drop  of  blood  be 
taken  from  the  finger,  by  pricking  with  a  needle  (the  triangu- 
lar or  glover's  is  the  best),  it  will  be  seen 
after  a  time  that  the  exterior  of  the  corpus- 
cle is  indented  or  crenated,  as  this  change 
is  called.  It  is  well  shown  in  Fig.  20. 

Examination  of  the  circulation  in  the 
web  of  a  frog's  foot. — Take  a  medium-sized 
frog  and  curarize  him  by  injecting  beneath       Plo  2o -Human 
the  skin,  with  an  ordinary  hypodermic  syr-    £dt ™v°*** crenated-  <R° 
inge,  two  drops  of  a  weak  solution  of  curara 
(1—2,000  in  water)  or  a  few  minims  of  a  50  per  cent,  solution 
of  chloral  hydrate  (Schaefer).     After  a  variable  time  the  ani- 
mal will  be  completely  paralyzed,  but  the  circulation  will  go 
on  as  before. 


There  are  many  difficulties  in  the  use  of  curara,  depending  on  the  variable 
strength  of  the  drug,  the  idiosyncrasies  of  the  animal,  and  other  causes  that 
we  do  not  appear  to  understand.  A  solution  which  will  produce  a  proper 
amount  of  paralysis  in  a  frog  on  one  day  will  rapidly  kill  another  frog  the  next 
day.  To  ensure  any  reliability  of  action,  it  is  well  to  have  a  specimen  of 
which  the  strength  has  been  properly  tested.  Then,  if  time  enough  is  at  one's 
disposal,  a  weak  solution,  such  as  the  above,  may  be  injected  every  hour  until 
the  symptoms  of  the  drug  are  apparent.  If  the  subsequent  recovery  of  the 
animal  is  not  of  vital  importance,  the  amount  may  be  increased,  for  the  circu- 
lation will  often  be  well  shown,  even  if  the  animal  does  not  eventually  survive. 

My  friend,  Dr.  W.  H.  Welch,  who  is  in  charge  of  the  Histological  Labora- 
tory at  the  Bellevue  Medical  College,  employs  a  watery  solution  of  curara. 
He  keeps  on  hand  a  |  per  cent,  solution  of  the  drug  (  1  gramme  to  200  c.c.  of 
distilled  water),  and  then  dilutes  it  as  occasion  may  warrant  to  i  per  cent.,  or 
even  -^  per  cent.  (1—500  or  1—1,000).  Of  this  diluted  solution  he  injects  four 
or  five  drops  into  the  dorsal  lymph- sac  of  the  frog.  A  still  more  dilute  solu- 
tion he  is  often  in  the  habit  of  using,  so  that  the  frog  does  not  come  under  the 
influence  of  the  drug  for  an  hour  or  an  hour  and  a  half.  After  twenty-four  to 


46  MANUAL    OF    HISTOLOGY. 

forty-eight  hours  the  animals  entirely  recover,  but  if  a  stronger  solution  is 
used,  he  finds  the  results  are  frequently  fatal,  though  the  animals  may  survive 
long  enough  to  permit  a  ready  demonstration  of  the  circulation,  emigration  of 
leucocytes,  etc. 

Now  envelop  Ms  body  in  a  damp  cloth  and  extend  him  upon 
a  cork  plate  about  a  quarter  inch  thick  and  large  enough  to 
support  the  entire  body.  Make  a  small  opening  in  the  cork, 
and  over  it  place  the  web  of  the  frog's  foot,  fastening  the  latter 
by  ordinary  pins. 

The  circulation  may  in  this  way  be  studied  at  one' s  leisure. 
The  red  and  white  blood-corpuscles  are  seen  in  the  arteries, 
veins,  and  capillaries.  While  the  red  bodies  pass  rapidly 
through  the  central  portions  of  the  vessels,  the  white  creep 
slowly  along  the  walls,  altering  their  shape  as  they  meet  with 
any  obstruction.  Where,  however,  a  small  artery  divides,  it 
will  sometimes  be  seen  that  the  corpuscles,  especially  the  red, 
are  caught  at  the  bifurcation ;  parb  bending  to  go  down  one 
branch,  and  part  down  the  other  ;  taking,  in  fact,  the  shape  of 
a  saddle-bag.  Such  a  phenomenon  exhibits  the  elastic  and 
distensile  properties  of  the  corpuscle.  Apply  an  irritant,  such 
as  a  weak  solution  of  nitrate  of  silver,  and  after  prolonged  and 
careful  watching,  the  gradual  exit  of  both  white  and  red  cor- 
puscles may  be  seen.  This  procedure  requires  extreme  pa- 
tience and  a  co-operation  of  peculiarly  fortunate  conditions, 
which  are  not  likely  to  favor  the  beginner  in  microscopy. 

Internal  structure  of  the  red  corpuscles. — As  yet  the  inti- 
mate structure  of  blood-corpuscles  is  a  matter  little  understood, 
though  an  abundance  of  theories  are  rife  about  it.  Klein  main- 
tains that  these  corpuscles,  in  common  with  others  in  the  body, 
are  traversed  by  an  intracellular  network.  In  the  red  cor- 
puscles of  the  newt,  especially,  he  says  there  is  a  network  of 
fibrils,  with  an  interfibrillar  hyaline  ground  substance,  both 
together  forming  the  so-called  stroma.  The  nucleus  contains  a 
network  of  fibrils  in  connection  with  the  network  of  the  cor- 
puscle proper ;  the  haemoglobin,  a  colored  fluid,  is  contained  in 
the  substance  of  the  meshes  of  the  network  of  the  corpuscle 
proper.  Drs.  Cutter,  of  Boston,  and  Heitzmann,  of  this  city, 
also  state  that  there  is  an  intracellular  network.  The  former 
regards  it  as  due  to  the  mycelium  of  a  parasitic  growth. 

Dr.  Elsberg,  of  this  city,  also  states  that  he  finds  a  reticu- 
lar  appearance  after  using  a  solution  of  the  bichromate  of 


THE    BLOOD.  47 

potash  (30  per  cent,  to  50  per  cent,  of  a  saturated  solution  in 
water). 

Real  granules  are  often  present  in  the  corpuscles,  as  may  be 
proved  by  adding  water  in  large  quantity.  They  will  then 
become  greatly  distended,  and  bursting,  the  granules  will  be 
scattered  throughout  the  field. 

If  finely  ground  vermilion  is  sprinkled  in  the  liquid,  some 
of  the  white  corpuscles  will  take  up  the  granules,  perhaps  with- 
out losing  their  amoeboid  character  ;  finally,  they  may  eject 
them  after  a  longer  or  shorter  sojourn. 

According  to  Boettcher,  the  human  red  blood-corpuscle  has  a  nucleus.  He 
exhibits  it  in  the  following  way :  Taking  a  saturated  solution  of  corrosive  subli- 
mate in  alcohol  (96°),  he  diffuses  about  fifty  volumes  with  one  of  blood.  The 
corpuscles  are  deprived  of  their  hsematin,  but  at  the  same  time  are  preserved. 
The  mixture  is  frequently  agitated,  but  in  about  twenty-four  hours  it  is  allowed 
to  subside,  when  the  superincumbent  fluid  is  poured  off  and  alcohol  added. 
By  further  agitation  for  another  twenty-four  hours  the  corpuscles  are  thoroughly 
washed,  and  then  settle  at  the  bottom  of  the  vessel.  Prof.  Boettcher  claims 
in  this  way  to  have  found  three  classes  of  red  globules.  The  first  are  homo- 
geneous and  shiny  throughout ;  the  second  are  clear  externally,  but  granular 
within ;  the  third  variety  exhibit  a  nucleus  and  nucleolus. 

Development  of  ike  Hood-corpuscles. — In  early  foetal  life 
all  the  corpuscles  are  colorless  (Klein).  According  to  Balfour 
and  Foster,  both  colored  and  colorless  corpuscles,  at  least  in 
the  chick,  are  developed  from  solid  sprouts  of  protoplasm,  de- 
rived from  the  middle  germinal  layer.  There  seems  good  rea- 
son, however,  to  believe  that  the  leucocytes  are  formed  in  part, 
at  least,  from  the  lymphatic  glands,  and  Klein  thinks  that 
they  are  thrown  off  from  the  "germinating  buds"  of  serous 
membranes.  Later,  the  red  ones  make  their  appearance,  and 
for  a  time  are  nucleated.  The  investigations  of  Neumann  and 
Bizzozero,  showing  that  the  red  corpuscles  in  the  medulla  of 
bones  are  also  nucleated,  favors  the  theory  that  bone-marrow  is 
one  of  the  theatres  for  such  corpuscular  metamorphosis. 

According  to  Hayem  the  production  of  red  corpuscles  in  the 
blood  is  accomplished  through  the  agency  of  hcematoblasts, 
i.e.,  minute  red  corpuscles.  In  convalescence  from  acute  fe- 
vers, or  after  a  considerable  loss  of  blood,  these  smaller  bodies 
may  be  observed  in  the  blood  for  a  variable  time,  even  some 
weeks. 


48  MANUAL    OF    HISTOLOGY. 

According  to  Recklinghausen,  the  colorless  corpuscles  may  be  generated 
from  the  red  corpuscles,  but  it  is  probable  that  they  may  be  formed  in  the  tis- 
sues at  many  points,  and  the  connective  substances  through  their  intimate  asso- 
ciation with  the  lymphatics  are  capable  of  manufacturing  them  in  almost  any 
quantity.  Neither  of  the  two  varieties  of  corpuscles,  the  red  or  the  white,  have 
a  cell-wall  or  outer  investing  membrane  that  can  be  demonstrated,  though  it  is 
not  unlikely  that  the  outer  layer  of  protoplasm  has  greater  density  than  the 
more  internal  portions. 

Wliite  or  colorless  blood- corpuscles. — The  white  blood-cor- 
puscle is  much  larger,  on  an  average,  in  the  human  species, 
than  the  red.  It  is  rounded  in  form,  and  is  estimated  as  varying 
between  .0077  and  .0120  mm.  The  average  is  .0091  mm.  (Frey). 
In  contour  they  are  apt  to  be  more  or  less  rough,  and  exhibit 
processes.  In  some  of  these  corpuscles  the  nucleus  is  distinct, 
though  when  quite  fresh  a  nucleus  is  rarely  seen.  If  the  eye 
of  the  observer  can  watch  the  corpuscle  when  it  is  upon  a 
heated  stage  and  under  suitable  conditions,  its  division  may 
be  seen.  The  number  contained  in  the  system  is  variable,  as 
we  shall  see,  depending  upon  a  great  number  of  conditions. 

The  personal  observations  of  the  author  do  not  incline  him 
to  regard  the  network  which  has  attracted  so  much  attention 
of  late  years  as  satisfactorily  shown  to  exist  in  living  corpus- 
cles, although  there  is  no  question  but  that  it  has  been  seen  in 
corpuscles  after  exposure  to  chemical  reagents. 

According  to  Dr.  Richard  Norris,  there  is,  in  mammals,  a  third  corpuscular 
element  which  is  usually  invisible  and  of  the  same  size  as  the  red  ones.  Some 
doubt  is  thrown  upon  his  alleged  discovery,  by  the  fact  that  the  method  he 
employs  is  likely  to  produce  artificial  appearances,  and  therefore  leads  to  the 
supposition  that  the  alleged  bodies  were  merely  red  corpuscles  decolorized. 

Mode  of  counting  the  blood-corpuscles. — Thanks  to  the 
instruments  of  Malassez,  Hayem  and  Nachet,  and  Gowers,  we 
are  in  a  position  to  count  the  red  blood-corpuscles  with  a  fair 
degree  of  accuracy. 

The  methods  are  somewhat  different,  but  are  not  difficult  to 
understand. 

Schaefer  describes  his  plans  as  follows  :  In  order  to  separate 
the  corpuscles  and  prevent  coagulation,  the  blood  used  is  first 
diluted  to  a  definite  extent — say  a  hundred  times — with  a  10 
per  cent,  solution  of  sulphate  of  soda.  The  mixing  can  be  per- 
formed in  a  measuring-glass  if  the  blood  is  in  sufficient  quan- 


THE    BLOOD.  49 

tity,  but  if  only  a  small  drop  is  obtainable,  such,  for  example, 
as  is  got  by  pricking  the  linger,  a  mixer  is  better.  This  con- 
sists of  a  capillary  tube  terminating  in  a  bulb,  the  capacity  of 
the  bulb  between  the  marks  1  and  101  being  exactly  100  times 
that  of  the  tube  from  its  point  to  the  mark  1.  A  small  glass 
ball  is  inclosed  in  the  bulb,  and  serves,  by  its  movements,  to 
facilitate  the  mixing.  The  capillary  tube  is  allowed  to  fill  with 
blood  as  far  as  the  mark  1 ;  sulphate  of  soda  solution  is  then 
sucked  up  as  far  as  the  mark  101.  As  it  passes  in,  it  of  course 
pushes  the  blood  before  it  into  the  bulb,  and  the  two  are  there 
thoroughly  mixed  by  gentle  agitation. 

The  next  thing  is  to  count  the  corpuscles  in  a  known  quan- 
tity of  the  mixture.  The  most  convenient  plan  is  that  of 
Hayem  and  Nachet.  A  slide  is  used,  having  a  glass  ring  -J-  mm. 
in  depth,  cemented  on  to  its  upper  surface.  A  drop  of  the 
mixture,  but  not  enough  to  fill  the  cell  so  formed,  is  placed  in 
the  middle  of  the  ring,  and  a  perfectly  flat  cover-glass  is  so  laid 
on  that  the  drop  touches  and  adheres  to  it  without  reaching 
the  sides  of  the  cell.  The  slide  is  placed  on  the  microscope, 
and  as  soon  as  the  corpuscles  have  settled  down  to  the  bottom 
of  the  drop,  the  number  in  a  definite  area  is  counted.  If  the 
area  chosen  is  -J-  mm.  square,  this  will  give  the  number  which 
were  contained  in  |  mm.  cube  of  the  mixture,,  and  multiplying 
this  by  the  number  of  times  the  blood  was  diluted,  the  result 
will  be  the  number  of  corpuscles  in  -§-  mm.  cube  of  blood. 
Schaefer  thinks  that  it  is  more  convenient  to  have  the  quad- 
ratic markings  upon  the  micrometer  glass  of  the  eye-piece  than 
upon  the  slide,  which  is  a  practical  point.  The  quadratic 
markings  are  shown  in  Fig.  22.  To  measure  any  square,  it  is 
only  necessary  to  take  the  stage  micrometer,  ruled  in  milli- 
metres and  decimals,  and  adjusting  the  draw  tube,  make  the 
side  of  one  square  correspond  exactly  to  an  interval  of  |  mm. 
on  the  stage  micrometer.  It  will  then  be  convenient  to  mark 
the  tube  at  this  point,  and  then,  in  all  subsequent  work,  if  the 
tube  be  kept  at  this  line  and  a  slide  is  used  of  the  thickness  of 
the  micrometer  and  the  same  lens  and  eye -piece,  the  side  of  a 
square  will  always  be  |  mm.  This  method  is  the  one  in  general 
use. 

Another  less  frequently  employed  is  that  of  Malassez,  which 
is  also  described  by  Schaefer  as  follows  :  A  little  of  the  mixture 
of  blood  and  sulphate  of  soda  is  transferred  to  a  very  fine  flat- 


50 


MANUAL    OF    HISTOLOGY. 


tened  capillary  tube,  the  capacity  of  a  given  length  of  which  has 
been  ascertained  previously  and  marked  on  the  slide  to  which 
the  tube  is  fixed.  Thus,  in  his  capillary  tube  a  length  of  400  mi- 
cromillimetres  represents  the  T^V.^  Part  °f  a  cubic  millimetre 
of  the  mixture.  The  counting  is  performed  with  the  aid  of  a 
squared  ocular  micrometer,  the  microscope  tube  having  been 
previously  so  adjusted  by  the  aid  of  a  stage  micrometer  that 
the  side  of  the  square  shall  have  the  value  of  one  of  the  lengths 
(400  n l  for  example)  marked  on  the  slide.  The  result  of  the 


FIG.  21. — Hayem  and  Nachet's  apparatus  for  blood-counting. 

counting  gives  the  number  of  corpuscles  in  a  known  quantity 
(TBT.-S  c.mm.)  of  the  mixture,  and  the  number  in  a  whole  cubic 
millimetre  can  therefore  be  readily  determined. 

Dr.  Keyes  uses  a  modification  of  the  method  of  Hayem  and 
Nachet,  making  a  dilution  of  1  to  250,  in  order  to  render  the 
counting  more  easy.  In  Fig.  21  the  pipette,  A,  is  filled  up  to 
the  mark,  5  D  ;  it  is  then  emptied  into  the  glass  vessel,  F.  The 
pulp  of  the  finger  of  the  patient  whose  blood  is  to  be  tested 
should  be  pierced  with  a  triangular  needle  (glover's).  Quick 


A  micromillimetre  (O  = 


THE    BLOOD. 


51 


but  firm  pressure  down  the  finger  will  at  once  force  out  a  drop 
from  the  punctured  spot.  The  blood  must  be  drawn  imme- 
diately into  the  capillary  pipette  lest  it  coagulate.  When  the 
pipette  is  full  to  the  mark  2,  its  point  should  be  rapidly  wiped 
clean  of  any  blood  adhering  to  the  outside,  and  the  contents  at 
once  blown  into  the  artificial  serum  in  the  cup,  F.  A  little 
suction  back  and  forth  clears  the  tube  of  any  blood-corpuscles 
which  may  have  adhered  to  the  glass  within.  Both  tubes 
should  be  carefully  washed  before  being  put  away. 

The  mixture  is  now  to  be  thoroughly  agitated  with  the  glass 
rod,  and  before  it  has  time  to  settle,  a  drop  is  placed  in  the 
middle  of  the  cell  on  the  slide,  D,  care  being  taken  that  the 
drop  is  not  large  enough  to  touch  any  part  of  the  circumference 
of  the  cell.  The  covering  glass,  E,  should  at  once  be  placed 
upon  the  cell.  Should  the  drop  be  too  large,  so  that  when  the 
thin  cover  is  adjusted  it  spreads  out  too  much,  the  glass  should 
be  cleansed  and  the  attempt  made  anew.  Finally,  a  small  drop 
of  water  or  saliva  is  applied  to  the  edge  of  the  covering  glass, 
under  which  it  circulates  around  the  top  of  the  cell,  serving  to 
hold  the  cover  in  place  and  pre- 
vent evaporation.  The  slide  is 
then  put  in  position  and  when 
the  corpuscles  have  all  settled 
to  the  bottom  of  the  fluid,  the 
counting  should  begin.  The 
following  detailed  plan  is  then 
given  by  Dr.  Keyes  : 

"It  is  better  to  count  each 
of  the  sixteen  squares  and  write 
down  its  number  separately, 
so  that  in  counting  the  square 
beneath  it,  should  there  be  any 
doubt  about  counting  a  given 
corpuscle  lying  upon  the  line,  a  glance  at  the  number  recorded 
for  the  square  above  may  remove  all  doubt.  Many  corpuscles 
will  be  found  lying  upon  the  outside  lines  bounding  the  large 
square.  I  have  adopted  the  rule  of  rejecting  all  those  lying 
upon  the  upper  and  right-hand  outside  lines  (of  the  large 
square)  and  counting  all  those  lying  on  the  lower  and  left- 
hand  outside  lines. 

After  having  thus  obtained  the  number  of  red  corpuscles 


FIG.   22. — Blood  corpuscles    as    seen  with  the 
squared  ocular  micrometer.    (Keyes.) 


02  MANUAL    OF    HISTOLOGY. 

situated  within  the  large  square,  it  becomes  easy,  by  a  simple 
equation,  to  find  the  number  in  a  cubic  millimetre.  A  single 
count,  however,  exposes  to  sources  of  error,  and  in  order  to 
approach  more  nearly  to  exactness,  I  have  uniformly  counted 
the  number  contained  in  the  large  square  in  five  different  por- 
tions of  the  field  (sometimes  ten),  and  have  taken  a  mean  of  the 
whole  number  of  counts  as  the  standard. 

The  computation  is  as  follows  :  The  glass  cell  on  the  slide 
is  %  mm.  deep.  The  eye-piece  micrometer  marks  off  -§-  mm. 
square,  therefore  the  count  of  red  corpuscles  (or  white,  as  the 
case  may  be)  must  indicate  the  number  contained  (in  the  dilu- 
tion used)  in  -J-  mm.  cube.  But  J  mm.  cube  is  -^  of  a  c.mrn., 
therefore  the  number  counted  must  be  multiplied  by  125  ;  and 
the  blood  was  diluted  by  adding  250  parts  of  fluid  to  1  of  blood 
(2  c.mm.  to  500  c.mrn.),  therefore  the  product  above  obtained 
must  be  again  multiplied  by  251  to  get  the  number  of  corpus- 
cles in  a  c.mm.  of  pure  blood.  Instead  of  multiplying  twice,  a 
single  multiplication  by  the  product  of  125  x  251,  31,375,  will 
give  the  same  result." 


This  method  should,  theoretically,  be  absolutely  accurate,  but  there  are  vari- 
ous errors  which  will  unavoidably  creep  in.  First  of  all,  the  tubes  should  be 
verified  as  to  accuracy.  This  has  been  done  for  me  at  the  Winchester  Observa- 
tory, of  Yale  College,  by  Leonard  Waldo,  Esq.,  the  astronomer  in  charge.  My 
larger  glass  tube  is  slightly  different  in  shape  from  the  one  here  represented,  and 
is  marked  so  that  the  line  at  ^  indicates  a  capacity  of  500  cubic  millimetres 
(0.5005  grammes  of  distilled  water  at  26.4°  C.).  The  cubical  contents  of  the 
reservoir  from  the  point  to  the  line  i-  =  0.2425  +  0.008  =  2505  grammes  = 
250  c.mm.,  approximately.  Accordingly,  the  marks  ±  and  £  indicate  i  and  -J- 
a  cubic  centimetre,  within  a  limit  of  error  so  small  as  to  be  practically  insensi- 
ble. The  smaller  glass  tube,  which  is  capillary,  is  marked  2,  2£,  4,  and  5. 
The  level  5  indicates  a  capacity  of  5  c.mm.  The  capacity  between  the  pointed 
extremity  and  2  is  2  c.mm.,  less  Vfn  c.mm. ;  the  space  between  2  and  2|  con- 
tains .55  c.mm. ;  the  space  between  2£  and  4  contains  1.45  c.mm. ;  the  space 
between  4  and  5  contains  exactly  1  c.mm.  (Waldo).  The  determination  of  these 
capacities  was  made  by  using  distilled  water,  and  comparing  the  weight,  when 
filled  to  the  various  levels,  with  the  same  tube  after  careful  drying. 

These  estimates  are  given  to  show  one  of  the  errors  which  may  be  met 
with,  and  that  an  instrument,  before  using,  should  be  verified  by  some  one  who 
has  special  means  for  determining  capacities  of  this  kind.  My  eye-piece  mi- 
crometer was  made  for  me  by  Rogers,  of  Cambridge,  and  the  entire  field  was 
subdivided  into  squares,  so  that  every  portion  of  it  may  be  counted  without 
moving  the  slide.  My  method  has  been  practically  the  same  as  that  of  Dr. 
K3jes,  except  that  I  prefer  diluting  with  one  thousand  parts  of  the  diluent, 


THE    H^EMOCHROMOMETER.  53 

and  use  iodized  serum  in  place  of  urine.     The  ordinary  £  per  cent,  solution 
of  common  salt  in  water  will  also  answer  sufficiently  well. 

Kecent  investigations,  such  as  those  conducted  by  Drs.  Cut- 
ter and  Bradford,  of  Boston,  have  established  that  there  is 
great  variation  in  the  number  of  globules  of  an  individual,  de- 
pending on  various  causes,  such  as  the  locality  from  which  the 
blood  is  drawn,  the  loss  of  fluids,  as  by  diarrhoea,  sweating, 
increased  urinary  secretion,  etc.,  and  even  the  period  of  the 
day,  week,  or  year.  These  general  conclusions  have  also  been 
sustained  by  Hayem,  of  Paris,  in  researches  which  are  still 
being  prosecuted. 

When  one  further  considers  that  we  have  no  definite  stand- 
ard of  comparison ;  that  the  instrument  is  apt  to  be  imperfect ; 
that  there  is  a  liability  of  errors  to  the  amount  of  10  per  cent.; 
that  skill  and  practice  are  required  in  manipulation,  it  is  by  no 
means  difficult  to  see  that  the  haematometer  is  not  calculated 
at  present  to  introduce  much  scientific  precision  into  medicine, 
unless  the  most  extraordinary  precautions  are  taken  in  every 
case,  and  these  all  duly  noted. 

Blood  crystals. — The  pigment  of  the  blood  occurs  usually 
in  an  amorphous  form,  and  is  called  haematine.  The  brownish 
red  needles  found  in  extravasated  blood  are  known  as  haema- 
toidine. 

Haemoglobin  also  occurs  in  most  mammalian  blood,  and  is 
deposited  under  the  form  of  rhombic  plates.  It  is  estimated 
that  about  125  grammes  are  present  in  the  blood  of  a  healthy 
adult. 

THE   HJEMOCHROMOMETER. 

According  to  Mantegazza  and  others,  richness  in  haemoglo- 
bin indicates  a  corresponding  richness  in  red  corpuscles,  and 
any  special  depth  of  color  in  the  blood  may  be  regarded  as  im- 
plying a  certain  given  number  of  red  corpuscles  to  the  cubic 
millimetre.  While  this  ratio  appears  to  hold  true  in  health,  it 
fails  in  disease.  Thus,  a  condition  which  we  recognize  as  anae- 
mia may  be  almost  wholly  due  to  a  loss  of  haemoglobin  in  the 
corpuscle,  or  an  actual  loss  of  red  corpuscles,  together  with  a 
diminished  amount  of  haemoglobin  in  those  that  remain.  In 
the  cachexia  of  cancer  the  number  of  the  corpuscles  may  be 
sustained,  but  their  haemoglobin  diminished.  In  diabetes  mel- 


54:  MANUAL    OF   HISTOLOGY. 

litus,  on  the  other  hand,  there  may  be  an  excess  of  red  cor- 
puscles, while  there  is  a  diminution  of  their  haemoglobin.  In 
anaemia,  from  hemorrhage,  there  is  an  actual  loss  both  of  cor- 
puscles and  of  haemoglobin  in  those  that  remain. 

To  facilitate  the  estimation  of  haemoglobin,  an  instrument 
has  been  devised  by  Malassez  and  Verick  (Paris),  called  the 
TicemocTiroinometer,1  which  is  easily  manipulated,  and  bids  fail- 
to  establish  some  facts  of  practical  utility  (see  Archives  de 
Phys.,  1877,  p.  1). 

It  consists  of  a  hand-screen,  to  which  a  movable  prismatic 
trough,  containing  a  colored  fluid,  is  attached,  and  a  modified 
Potain  pipette.  By  means  of  this  apparatus  the  richness  of 
the  blood  in  haemoglobin,  and  the  maximum  quantity  of  oxy- 
gen which  it  can  absorb,  may  be  determined.  To  use  the  ap- 
paratus the  pipette  is  first  filled  up  to  a  certain  point  with  the 
blood  to  be  examined,  and  then  diluted  with  100  parts  of  water. 
The  reservoir  of  the  pipette  is  then  filled  with  the  diluted 
blood.  The  screen  has  two  holes;  behind  one  of  these  the 
prismatic  trough  is  made  to  slide  up  and  down,  the  color  of  the 
fluid  contained  in  it  of  course  varying  in  intensity,  according 
to  the  extent  of  the  upward  and  downward  motion.  Behind 
the  other  opening  the  reservoir  of  the  pipette  is  secured  by 
means  of  a  little  elastic  ring.  The  screen  is  now  held  against 
the  light  (preferably  white  light ;  sunlight  is  to  be  especially 
avoided),  and  the  trough  moved  until  the  color  of  the  blood 
mixture  is  matched  by  its  own  color.  Then  the  figure  on  the 
scale  attached  to  one  side  of  the  trough  is  read  off,  arid  this 
indicates,  by  reference  to  the  table  annexed  to  the  apparatus, 
the  points  to  be  determined.  If  the  blood  to  be  examined  be 
deeply  colored,  the  aqueous  blood-mixture  is  made  in  the  pro- 
portion of  £  to  100  ;  if  it  be  but  slightly  colored,  in  the  propor- 
tion of  2  to  100. 


BIBLIOGRAPHY. 

WELCKER.     Pragervierteljahreschr.     XLIV.,  p.  60.     1854.     Zeitschr.  f.  rat.  Med. 

3,  XX.,  p.  280. 

SCIIULTZE,  MAX.  Archiv  f.  mikrosk.  Anat.  I.,  p.  35.  1865. 
KOI.LETT.  Strieker's  Manual  of  Histology.  New  York,  1872. 
WOODWARD.  Ara.  Jour,  of  the  Med.  Sci.,  Jan.,  1875.  N.  Y.  Med.  Rec.,  Jan.  31, 1880. 


1  To  be  obtained  of  J.  F.  Reynders  &  Co.,  New  York  city. 


BIBLIOGKAPHY.  55 

KELSCH.     Arch,  de  Phys.     Vol.  II.     1875. 

KEYES.     Am.  Jour,  of  the  Med.  Sci.,  Jan.,  1876. 

HEITZMANN.     New  York  Med.  Jour..  April,  1877. 

MANTEGAZZA.     Berl.  Klin.  Woch.,  April  1,  1878. 

RANVIER.     Traite  technique  d'histologie.     Paris,  1877  et  seq. 

HAYEM.     Archives  de  Phys.     2  Ser.,  T.   VI.,  p.  201  et  seq.     1879. 

BIZZOZERO,  G.,  and  SALVIOLI,  G.     Centralb.  f.  d.  Med.  Wiss.     16,  p.  273.     1879. 

POUCHET.     Gaz.  Med.  de  Paris.     14,  16.     1879. 

CUTLER,  E.  G.,  and  BRADFORD,  E.  H.     Journal  of  Phys.     Vol.  I.    1878—1879. 

BOETTCHER.     Archiv  f.  raikrosk.  Anat.     Bd.  XIV.  p.  73.     1877. 

KL'EIN  and  E.  NOBLE  SMITH.     Atlas  of  Histology.     1879. 

ELSBERG.     Annals  of  the  N.  Y.  Academy  of  Sciences.  Vol.  I. ,  Nos.  9  and  10.    1879. 

(A  very  extensive  bibliography.) 

SATTERTHWAITE,  T.  E.     Arch,  of  Comp.  Med.     N.  Y.     II.     1880. 
BAXTER  and  WILLCOCK.     Lancet,  March  6,  13,  20,  1880. 


CHAPTER  IV. 

EPITHELIUM. 

THE  skin,  mucous  surfaces  of  the  body  and  various  pas- 
sages in  connection  with  them,  are  evenly  coated  with  bodies 
of  peculiar  shape,  which  are  united  together  to  form  a  cover- 
ing of  one  or  more  layers. 

In  some  places,  as  upon  the  external  portions  of  the  epider- 
mis, the  corpuscles  are  more  or  less  flattened.  Elsewhere,  as  in 
the  ducts  of  secreting  glands  and  in  the  trachea  and  fallopian 
tubes,  they  are  cylindrical,  and  the  free  extremities  are  often 
surmounted  by  cilia — fine,  hair-like  processes,  which  have  a 
vibratile  movement  that  propels  solid  matters,  such  as  sputa 
and  ova,  in  some  special  direction.  In  other  parts,  again,  as  in 
the  collecting  tubes  of  the  kidney,  near  the  apices  of  the  pyra- 
mids, a  cuboidal  variety  is  found.  Intermediate  or  transitional 
forms  are  also  frequently  met  with  in  all  parts  of  the  body. 

A  characteristic  of  epithelium  which  is  especially  note- 
worthy is  that  the  same  species  is  not  found  uniformly  in  the 
same  position.  Sometimes  this  mutation  of  type  is  governed 
by  the  physical  laws  that  regulate  the  growth  and  development 
of  the  subject,  or  it  may  be  a  consequence  of  disease.  An  ex- 
ample of  the  former  peculiarity  is  to  be  noted  in  the  larynx, 
where  the  ciliated  corpuscles  of  infancy  part  with  their  cilia 
from  advancing  age,  or  indeed  may  become  flattened. 

As  an  example  of  pathological  change  it  is  not  uncommon 
to  find  villosities  covered  with  the  most  beautifully  marked 
cylindrical  epithelium,  springing  from  the  ordinary  mucous 
membrane,  just  where  the  superficial  corpuscles  happen  to  be 
somewhat  flattened  in  their  normal  state. 

The  use  to  which  the  part  is  put  has  also  an  important  influ- 
ence in  governing  the  shape  and  other  attributes  of  the  corpus- 
cles. Where  they  are  exposed  to  the  drying  action  of  the  air, 
to  harsh  usage,  and  continued  friction,  as  upon  the  hands  and 


EPITHELIUM.  57 

feet,  they  become  flattened,  dry,  and  horny  ;  in  the  interior  of 
the  body,  on  the  other  hand,  where  such  conditions  do  not 
exist,  they  are  succulent  and  pliable. 

Ordinary  flattened  or  squamous  epithelium. — This  is  best 
obtained  by  scraping  the  back  of  one's  tongue  with  a  blunt 
instrument.  The  scrapings  should  then  be  mounted  in  equal 
parts  of  the  common  salt  solution  (J  per  cent.)  and  glycerine. 
The  epithelial  bodies  may  in  this  way  be  readily  studied.  They 
are  separate  or  grouped  together  in  collections  of  two  or  more. 
In  diameter  they  vary  between  ^TT  an&  T£TT  incn-  Tne  sur~ 
faces  are  all  bevelled,  and  at  the  same  time  are  uneven  or 
ridged ;  consequently  they  overlap  one  another  to  a  certain 
degree,  and  the  inequalities  of  one  corpuscle  fit  into  those  of 
another.  The  most  superficial  epithelium  is  the  thinnest,  and, 
conversely,  the  deepest  is  apt  to  be  the  most  nearly  spheroidal. 

Intermixed  in  the  mucus  will  be  seen  the  so-called  mucous 
or  salivary  corpuscles.  They  are  not  very  numerous,  but  are  de- 
tected by  the  "molecular"  or  Brownian  movement  of  their  in- 
terior. In  size  they  closely  resemble  the  white  corpuscles  of  the 
blood,  but,  as  a  rule,  exhibit  no  amoaboid  motion  ;  the  white  glob- 
ules, on  the  other  hand,  rarely  have  any  Brownian  movement. 

The  surfaces  of  the  epithelia  are  often  so  covered  with  bac- 
teria that  they  are  only  recognized  with  some  difficulty.  These 
little  bodies  are  wonderfully  uniform  in  size,  and  are  disposed 
in  the  most  regular  manner.  Looking  straight  down  upon 
them  they  appear  to  be  minute  spheres  with  a  diameter  aver- 
aging between  ^QT  and  ^TUTTF  incn-  Closer  inspection  and 
examination  of  the  corpuscles  at  their  free  edges  shows  that 
the  bacteria  are  in  reality  rod-shaped,  and  that  they  adhere  to 
the  corpuscles  by  their  extremities,  standing  in  such  cases 
vertical  to  the  surface.  A  high  power,  such  as  the  immersion 
TV,  develops  this  point  quite  clearly. 

Incidentally  the  mucin  of  the  mucus  may  be  seen  to  advan- 
tage in  the  scrapings  of  the  mouth  or  tongue.  To  a  drop  or  two 
add  another  drop  of  commercial  alcohol  and  a  drop  of  the  or- 
dinary hsematoxylin  solution.  The  alcohol  will  coagulate  the 
mucin,  which  then  takes  the  form  of  filaments  and  branching 
networks  ;  the  logwood  will  make  them  distinctly  visible. 

Epithelium  from  the  skin  may  be  studied  in  one  of  two 
methods.  Take  a  fresh  specimen  from  the  palmar  surface  of 
the  hand  or  plantar  of  the  foot,  freeze  it  in  a  section  cutter, 


58  MANUAL    OF   HISTOLOGY. 

take  off  a  thin  slice  with  a  knife,  immerse  for  a  few  seconds  in 
a  dilute  solution  of  acetic  acid  (J  per  cent.),  and  then  mount  in 
glycerine  and  water ;  or  a  similar  portion  of  the  skin  may  be 
steeped  in  a  weak,  sherry-colored,  watery  solution  of  the  bichro- 
mate of  potassium  (gr.  ij. — iij. — f.  §  j.)  for  several  days  and  then 
hardened  in  alcohol,  first  of  80  per  cent.,  then  of  90  per  cent., 
finally  of  95  per  cent,  strength  ;  this  latter  process  taking  several 
days,  and  ending  when  the  specimen  is  thoroughly  hard.  Sec- 
tions may  then  be  made  in  the  usual  way.  By  the  use  of  acetic 
acid  the  nuclei  will  readily  be  seen  in  the  lower  strata  of  the  epi- 
dermis, while  the  outermost  layers  have  none,  or,  at  least,  none 
that  can  be  demonstrated  by  the  usual  histological  methods. 

Three  different  strata  can  now  be  recognized  :  1,  the  stra- 
tum corneum,  or  corneous  layer,  in  which  the  corpuscles  are 
flattened,  and  appear  to  have  no  nuclei ;  2,  the  rete  mucosum, 
or  malpighian  layer,  immediately  underlying  the  former,  and 
composed  of  cuboidal  elements,  armed  with  spines  or  prickles, 
as  they  are  often  called  ;  lastly,  3,  there  is  the  pigmented  layer, 
which  overlies  the  papillae.  The  bodies  of  the  latter  corpuscles 
are  infiltrated  with  particles  of  melanine,  which  is  the  cause  of 
the  dark  color  in  the  skin  of  the  negro  and  swarthy  races. 

Maceration  of  the  epidermis  in  liquor  potassse  is  an  excellent 
method  for  exhibiting  the  individual  elements ;  after  a  few  min- 
utes they  will  swell  up  and  detach  themselves  from  one  another. 

It  was  thought,  until  quite  recently,  that  these  prickle  cells  interdigitate 
with  one  another,  but  Ranvier  has  claimed  that  they  are  continuous  with  those 
of  adjacent  corpuscles  (see  chapter  on  the  Skin).  This  point  is  difficult  to  set- 
tle, as  it  requires  a  special  method  and  lenses  of  high  power.  Ranvier  injected 
a  one-fourth  per  cent,  solution  of  osmic  acid  into  the  lower  layers  of  the  epider- 
mis, using  a  hypodermic  syringe,  and  driving  the  fluid  right  and  left. 

There  is  a  form  of  flattened  and  pigmented  epithelium  that 
may  be  seen  by  examining  the  external  surface  of  the  choroid, 
the  ciliary  processes,  and  the  posterior  surface  of  the  iris.  In 
the  choroid  these  bodies  look  like  a  mosaic  of  polyhedral  cells. 
Such  specimens  may  be  permanently  preserved  by  simply  dry- 
ing them,  and  then  mounting  in  dammar  or  Canada  balsam. 

Ciliated  epithelium. — The  movement  of  living  cilia  is  readily 
seen.  All  that  is  necessary  is  to  take  the  common  frog  (Rana 
temporaria),  draw  out  his  tongue,  and  then  observing  the  teat- 
like  projections  at  the  posterior  part,  snip  one  off. 


NC 
MEDICAL  SCHOUL  LiumA 

EPITHELIUM.  59 

This  little  piece  is  then  to  be  mounted  in  a  one-fourth  per 
cent,  salt  solution,  or  serum,  and  examined.  Along  the  free 
edge  of  the  mucous  membrane  the  cilia  will  be  seen  engaged  in 
active  vibratile  motion.  The  appearance  presented  by  a  broad 
expanse  of  moving  cilia  has  been  aptly  described  as  resembling 
a  field  of  grain  which  is  being  swept  by  the  wind,  though  the 
motion  is  often  much  more  rapid  than  this  comparison  would 
imply.  It  will  be  seen  that  various  substances,  such  as  blood 
globules,  are  propelled  in  a  definite  direction.  When  the  frog's 
mouth  is  open,  all  solid  particles  that  are  lodged  upon  the 
mucous  membrane  are  carried  quietly  but  inevitably  toward 
the  gullet,  and  down  toward  the  stomach.  The  power  of  the 
ciliary  movement  may  be  estimated,  in  a  measure,  by  placing 
some  light  but  adhering  body  upon  the  anterior  portion  of  the 
roof  of  the  mouth,  and  then  inverting  the  animal.  The  sub- 
stance immediately  begins  to  ascend  against  gravity,  and  soon 
is  wedged  in  the  gullet.  The  same  force,  though  acting  in  an 
opposite  direction,  expels  mucus,  pus,  and  indeed  all  solid 
matters,  from  the  cavities  of  the  human  lungs  ;  it  also  propels 
the  ova  through  the  Fallopian  tubes  into  the  uterus.  In  ex- 
cessive catarrh  from  mucous  membranes  the  epithelial  bodies 
may  themselves  be  expelled,  so  that  they  are  not  infrequently 
found  with  their  cilia  attached,  as  in  the  nasal  discharges.  After 
death  cilia  are  hard  to  recognize  ;  they  contract  down  to  little 
knobs  on  the  surface  of  the  cells,  and  can  only  be  demonstrated 
when  the  eye  looks  directly  down  upon  them.  Osmic  acid  is 
useful  to  preserve  them  in  their  natural  condition.  Take  a  fresh 
specimen  and  immerse  it  for  twenty-four  hours  in  a  one-fourth 
percent,  osmic  acid  solution,  and  for  another  twenty -four  hours 
in  dilute  alcohol ;  then  tease  and  mount  in  glycerine  and  water. 
It  will  be  observed  that  each  cilium  is  a  slim,  straight  rod,  which 
is  apparently  structureless  ;  they  rest  upon  a  band,  which,  with 
a  high  power,  may  be  seen  to  have  vertical  striations. 

Effect  of  reagents. — By  making  use  of  the  moist  chamber 
(Fig.  19,  p.  42),  and  placing  a  drop  of  chloroform  in  the  cor- 
ner of  the  cell,  it  will  be  seen  that  the  action  of  the  cilia  rap- 
idly stops,  while,  if  the  chloroform  be  removed,  it  will  again 
resume  its  activity. 

If  carbonic  acid  gas  is  admitted,  the  action  of  the  cilia  will 
at  first  be  accelerated,  but  subsequently  retarded,  and  eventu- 
ally stopped  (Kuehne). 


60  MANUAL    OF   HISTOLOGY. 

After  shutting  off  the  carbonic  acid  gas  and  admitting  oxy- 
gen, the  action  will  again  commence.  When  the  ordinary 
motion  has  ceased,  the  gradual  application  of  heat  will  cause 
it  to  return  ;  but  if  the  temperature  be  raised  continuously,  a 
point  will  soon  be  reached  where  the  excessive  heat  will  cause 
the  motion  again  to  stop. 

Columnar  or  cylindrical  epithelium. — This  is  the  epithe- 
lium^ar  excellence  of  the  digestive  tract,  clothing  the  mucous 
membrane  from  the  cardiac  orifice  of  the  stomach  to  the  anus. 
It  is  also  found  at  the  orifices  of  the  ducts  of  the  large  excretory 
glands,  such  as  the  liver  and  pancreas,  in  the  milk-passages  of 
the  nipple,  and  in  some  parts  of  the  generative  system.  These 
cells  are  tall  and  narrow,  standing  vertical  to  the  surface  of  the 
mucous  membrane.  Sometimes  they  are  broadest  at  their  free 
extremity,  at  other  times  about  the  middle,  so  that  when  viewed 
from  above  they  appear  to  be  separated  from  one  another.  The 
nuclei  are  rounded,  and  are  either  placed  about  the  middle  of 
the  cell  or  near  the  attached  border.  They  admit  of  consider- 
able variation,  however,  as  to  size  and  shape,  some  of  those  in 
immediate  contact  being  broad  at  one  extremity,  and  some 
broad  at  the  others  ;  the  free  edge  also  may  be  uneven. 

Scrape  the  surface  of  a  frog's  tongue  or  a  rabbit's  intestine 
after  washing ;  the  cells  will  be  seen  to  advantage.  Place 
some  of  the  scrapings  in  a  drop  of  glycerine  and  water  to 
which  another  drop  of  dilute  acetic  acid  (J  per  cent.)  has  been 
added,  and  mount.  In  this  way  the  nuclei  will  be  brought 
clearly  into  view.  The  cells  closely  resemble  in  their  shape 
the  columnar  variety,  except  that  they  have  no  cilia.  Among 
them  will  almost  always  be  found  chalice  or  goblet  cells.  They 
lie  among  the  columnar  corpuscles,  and  are  usually  shorter, 
but  broader,  expanding  in  the  centre,  and  terminating  at  their 
attached  extremities  in  a  single  or  double  process.  The  sur- 
face is  cupped.  They  contain  one  or  more  nuclei ;  whether 
they  are  a  distinctive  cell  or  not  is  as  yet  uncertain.  Some 
suppose  them  to  be  the  ordinary  columnar  cell  undergoing 
mucoid  degeneration ;  others  that  they  are  not  epithelial  at 
all.  Frey  regards  them  as  artificial  productions.1 

1  The  most  rational  explanation  is  that  furnished  by  F.  E.  Schultze.  The  intra- 
fibrillar  substance  is,  according  to  this  observer,  converted  into  hygroscopic  mucin, 
which  swells  up.  This  constitutes  a  change  in  the  cell  which,  from  being  columnar, 
becomes  goblet-shaped.  The  wall  finally  ruptures,  and  the  mucin  is  poured  out. 


EPITHELIUM.  61 

Other  varieties  of  epithelium  will  be  taken  up  in  connection 
with  the  different  organs.  As  already  stated,  many  transi- 
tional varieties  occur,  even  in  direct  association  with  the  typi- 
cal forms  we  have  described. 

Structure  of  epithelial  corpuscles. — According  to  the  views 
of  Heitzmann,  Klein,  and  others,  the  substance  of  the  cor- 
puscle is  pervaded  by  a  network,  the  minute  fibres  of  which 
may  be  seen  under  a  lens  of  high  power.  The  nucleus  or  cen- 
tral body  is  also  similarly  provided.  Within  the  meshes  of 
this  network  there  is  a  hyaline  substance,  the  abundance  or 
paucity  of  which  determines  the  size  of  the  meshes. 

The  "granules,"  which  have  often  been  described,  are,  ac- 
cording to  this  view,  the  nodal  points  of  the  mesh  work.  It 
is  also  stated  that  the  epithelial  cells  sometimes  have  a  fine 
limiting  membrane  (Klein)  ;  but  even  in  such  instances  it  IB 
merely  a  condensation  of  the  outer  part  of  the  corpuscle. 
Within  the  nucleus  there  are  also,  according  to  the  same  ob- 
servers, fibres,  within  the  meshes  of  which  are  not  infrequently 
real  granules  (nucleoli).  The  epithelial  corpuscles  are  at- 
tached together,  either  by  an  interlacement  of  their  processes, 
as  in  the  liver,  or  by  a  peculiar  cement  substance,  as  in  pave- 
ment epithelium,  or  by  a  continuity  of  their  processes,  as  in  the 
rete  mucosum. 

Recent  histological  studies  have  narrowed  the  field  formerly 
occupied  by  the  epithelial  bodies,  and,  in  accordance  with 
these  views,  the  flattened  corpuscles  which  cover  serous  mem- 
branes, such  as  the  pleura  and  peritoneum,  will  be  arranged 
under  the  connective-tissue  series,  rather  than  under  the  epi- 
thelial. The  reasons  for  this  change  will  be  given  in  a  subse- 
quent chapter. 


BIBLIOGRAPHY. 

SCHULTZE,  M.      Die  Stachel- und  Riffzellen.     Virchow's  Arch.,  Vol.  XXX.,  1864, 

p.  260. 

SCHULTZE,  F.  E.     Epithel.  u.  Driisenzellen.     Arch.  f.  mikrosk.  Anat.     1867. 
RANVIER.     Traite  technique  d'histologie.     Paris,  1875. 
DEL  AFIELD.     Studies  in  Pathological  Anat.     New  York,  1878  et  seq. 
KLEIN  and  E.  NOBLE  SMITH.     Atlas  of  Histology.     1879-80. 
HEITZMANN.     New  York  Medical  Record,  July  31,  1880,  p.  133. 
FREY.     The  Microscope  and  Microscopical  Technology.     New  York,  1880. 


CHAPTER  V. 

THE  CONNECTIVE  SUBSTANCE  GKOUP. 

MUCOUS  OR  GELATINOUS  TISSUE  ;  ADENOID  TISSUE  ;  NEUROG- 
LIA  ;  FAT  TISSUE  ;  FIBROUS  TISSUE  PROPER  ;  CORNEAL  TIS- 
SUE ;  INTERMUSCULAR  TISSUE  ;  TENDON  TISSUE  ;  ELASTIC 
TISSUE. 

THE  term  connective  substance  was  first  proposed  by  Reich- 
ert  in  1845,  and  is  now  applied  to  a  class  of  animal  tissues  whose 
offices  are  very  important  in  the  economy.  Prominent  among 
them  is  bone,  which  forms  the  solid  framework  of  the  body, 
gives  it  strength,  and  supplies  points  of  attachment  for  muscles 
and  tendons ;  another  group  comprises  the  ligaments,  which 
assist  in  holding  the  bony  parts,  and  also  some  organs,  in  their 
proper  relations  ;  others  again,  of  a  more  delicate  nature,  fur- 
nish support  or  protection  for  epithelial  bodies,  blood-vessels, 
and  nerves.  Just  at  the  present  time  the  histology  of  connec- 
tive substances  has  an  important  bearing  on  many  points  that 
relate  to  inflammation,  degeneration,  and  the  development  of 
certain  new  growths,  and  it  is  therefore  desirable  to  have  a  clear 
conception  of  them.  This  object  is  best  effected  by  studying 
each  variety  separately,  not  only  in  its  normal  condition,  but 
under  the  changes  it  exhibits  when  acted  on  by  the  factors  that 
are  concerned  in  the  processes  of  disease. 

It  is  a  property  of  these  substances  that  they  supplant  one 
another  at  different  times  or  under  peculiar  circumstances.  As 
an  example,  the  hyaline  cartilage  of  young  life  may  change 
into  true  bone  in  old  age,  while,  on  the  other  hand,  there  is 
always  a  tendency  for  fully  formed  tissue,  if  inflamed,  to  re- 
vert toward  the  embryonic  type. 

The  connective  substances  may  be  subdivided  as  follows : 
1,  mucous  or  gelatinous  tissue ;  2,  adenoid  tissue ;  3,  neurog- 


THE    CONNECTIVE    SUBSTANCE    GEOUP. 


63 


lia ;  4,  fat  tissue  ;  5,  fibrous  tissue  proper ;  6,  corneal  tissue ; 
7,  intermuscular  tissue ;  8,  tendon  tissue ;  9,  elastic  tissue ; 
10,  bone;  11,  cartilage;  12,  enamel;  and  13,  dentine.  The 
word  connective  tissue  was  first  proposed  by  Johannes  Mueller, 
and  is  sometimes  used  as  synonymous  with  connective  sub- 
stance, but  erroneously.  The  former  is  merely  a  variety  of  the 
latter,  and  is  usually  intended  to  indicate  one  or  other  of  the 
flexible  connective  substances  that  form  the  interstitial  material 
of  the  body,  and  in  that  sense  we  shall  use  it  for  convenience 
sake,  but  without  implying  any  special  histological  character. 

In  precise  histological  descriptions  it  is  always  best  to  use 
the  special  name  of  the  variety  intended,  such  as  mucous  tis- 
sue, adenoid  tissue,  and  the  like,  where  the  structure  happens 
to  be  known. 

It  is  also  well  to  state  here  that  the  term  "cellular"  tissue, 
found  in  many  of  our  anatomies,  is  apt  to  mislead  the  student. 
The  word  "cellular"  has  no  reference  to  cells,  i.e.,  corpuscles, 
but  to  the  large  cavities  or  spaces  that  exist  in  all  loose  connec- 


Fio  23.— Gelatinous  or  mncous  tissue.    Human  umbilical  cord. 

tive  tissues,  of  which  the  subcutaneous  is  an  example.  These 
spaces  are  easily  seen  by  the  naked  eye,  when  inflated  with  air. 

Mucous  or  gelatinous  tissue.— This  is  the  most  simple 
form  that  is  met  with.  It  is  seen  to  great  advantage  in  the 
embryonic  umbilical  cord,  which  also  contains  several  other 
varieties  of  connective  tissue. 

The  following  method  has  been  found  best  suited  to  demon- 
strate it.  Take  a  small  piece  of  cord  at  about  the  third  month 
and  immerse  it  a  few  weeks  in  Mueller' s  fluid  ;  make  a  thin  sec- 
tion through  the  very  soft  gelatinous  part,  then  soak  it  a  few 
minutes  in  distilled  water,  to  which  subsequently  a  few  drops 


64 


MANUAL    OF    HISTOLOGY. 


of  acetic  acid  are  to  be  added  so  that  the  solution  shall  not  con- 
tain more  than  1  per  cent,  of  acid,  and  then  mount  in  glyce- 
rine. It  will  then  be  seen  that  the  softest  portion  contains 
numbers  of  irregularly-shaped,  thin  plates,  some  provided  with 
an  oval,  flattened  nucleus,  others  having  none  that  are  appa- 
rent (Fig.  23).  Some  of  these  flattened  bodies  anastomose  by 
these  processes  with  those  of  other  plates,  others  are  quite  free. 
The  substance  tying  between  the  cells,  the  intercellular  sub- 
stance, is  quite  homogeneous,  or  slightly  granular,  in  the  softest 
portions,  and  has  at  first  no  defined  fibrillation.  In  the  neigh- 
borhood of  the  former  tissue,  lines  of  fibrillation  occur,  while  at 
the  same  time  these  flattened  bodies  become  smaller,  although 
they  are  still  flattened  (Fig.  24,  b).  Mucous  or  gelatinous  tissue, 


FIG.  24. — Connective  tissue  in  an  advancing  stage  of  development.    From  the  umbilical  cord. 

as  it  is  seen  in  the  umbilical  cord  of  an  embryo,  is  properly  an 
embryonic  or  developmental  form  of  connective  tissue  which  is 
never  found  in  normal  adult  life.  All  the  phases  of  develop- 
ment may  here  be  seen,  from  the  most  primitive,  comprised  in 
Wharton'  s  jelly,  to  the  firm,  fibrous  fascicles  that  encircle  the 
vessels. 

Properly  speaking,  the  true  mucous  tissue  is,  as  its  name 
implies,  a  viscid  material,  and,  indeed,  is  much  like  half-set 
glue,  in  which  the  corpuscles  are  scattered  with  little  or  even 
no  cohesion. 

The  intercellular  substance  differs  from  albumen  in  not  con- 
taining sulphur  ;  from  chondrin  and  gelatin,  in  not  being  pre- 
cipitated by  boiling,  tannin,  or  the  bichloride  of  mercury. 


THE    CONNECTIVE    SUBSTANCE    GROUP.  65 

At  an  early  stage  there  are  no  marks  of  fibrillations  in  the 
intercellular  substance,  but  later  fibrils  are  seen  in  the  vicinity 
of  the  corpuscles,  and  are  some  of  the  early  signs  that  organi- 
zation of  the  tissue  is  commencing. 

The  corpuscles  at  the  same  time  become  smaller,  and  about 
the  central  body  or  nucleus  we  see  a  delicate  expansion  (Fig. 
24  a\  which  is  the  envelope  of  the  connective-tissue  corpuscle— 
a  film  of  great  tenuity.  Klein  believes  that  in  these  corpuscles 
there  are  two  portions,  a  granular  or  firmer  part  continuous 
with  the  processes,  and  a  delicate  expansion  that  is  hardly 
visible.  It  is  certain  that  the  connective-tissue  corpuscle  is 
frequently  in  connection  with  one  or  more  of  its  fellows  by  a 
mutual  anastomosis  of  processes.  The  fibrillation  appears  to 
be  at  first  limited  to  certain  areas  about  the  cellular  elements, 
so  that  the  long,  flattened  and  pointed  lamellae  of  fibrous  tis- 
sues on  which  the  corpuscles  are  attached  look  like  large  cor- 
puscles with  correspondingly  large  nuclei.  Using  a  earners- 
hair  brush  and  pencilling  off  the  specimen  under  examination, 
after  soaking  in  a  10  per  cent,  watery  solution  of  common  salt; 
the  apparent  nuclei  with  their  delicate  envelopes  are  partially 
(Fig.  24  1))  or  wholly  removed.  We  then  see  small  strips  of 
more  or  less  fibrillated  tissue,  having  no  central  body  that  can 
be  recognized,  even  with  the  use  of  strong  staining  solutions. 
These  and  similar  observations  tend  to  establish  a  conviction 
that  the  fibrillated  portion  arises  from  the  soft,  gelatinous  ma- 
terial by  a  process  of  fibrillation  inaugurated  by  the  presence 
and  under  the  formative  action  of  the  connective-tissue  cor- 
puscle. It  is  not  impossible  that  the  fibrin  of  the  blood,  which, 
though  fluid  in  the  blood-current,  is  often  known  to  be  de- 
posited in  delicate  filaments,  may  contribute  largely,  if  not 
wholly,  to  the  formation  of  the  fibrillse.  As  the  tissue  becomes 
firmer,  the  little  plates  with  their  anastomosing  branches  form 
a  loose  network  which  separates  the  fibrils  into  distinctive 
bundles  or  fascicles,  and  encircles  them  more  or  less  completely. 

There  is  another  view  which  is  offered  as  an  explanation  of 
the  process  by  which  connective  tissue  becomes  organized.  It 
is  this.  The  change  is  derived  wholly  from  the  corpuscles. 
Some  of  them  split  up  into  fibrils,  constituting  the  fibrous 
part  of  the  tissue ;  the  others  remain,  and  are  developed  into 
connective-tissue  corpuscles.  This  view  has  the  support  of 
excellent  histologists. 

5 


00  MANUAL    OF    HISTOLOGY. 

The  white  corpuscles  of  the  blood  are  pre-eminently  suited 
for  building  tissue.  When  blood  is  organized,  which  occurs 
not  infrequently,  the  white  corpuscles  at  once  assume  an  im- 
portant role,  while  the  red  are  soon  melted  down  into  a  homo- 
geneous mass,  that  is  usually  absorbed.  This  change  is  ob- 
served under  various  pathological  conditions. 

Fibrous  tissue. — This  substance,  which  is  also  known  as 
fibril] ated  connective  tissue,  is  the  fully  developed  material 
that  has  just  been  described.  It  occurs  either  in  parallel 


FIG.  25.— Reticular  form  of  connective  tissue.    From  the  human  umbilical  cord. 

bundles  or  fascicles,  in  interlacing  lamellae,  or  as  a  fenestrated 
material  containing  larger  or  smaller  openings.  A  special  va- 
riety, the  reticular,  is  seen  to  great  advantage  in  the  umbilical 
cord  of  an  infant  at  birth  (Fig.  25). 

If  a  cut  be  carried  through  the  spongy  portions  of  the  cord, 
it  will  be  seen  that  the  tissue  is  composed  of  bright,  shining, 
branching  bundles,  <#,  superimposed  upon  which  are  a  num- 
ber of  oval,  flattened  plates,  a,  at  intervals ;  about  them  is 


THE    CONNECTIVE    SUBSTANCE    GROUP.  67 

a  delicate  envelope,  &,  which  appears  to  be  highly  elastic,  so 
that  it  will  stretch  or  relax,  according  as  the  networks  are 
compressed  or  dilated.  By  teasing  with  needles  or  immersion 
for  a  few  days  in  a  10  per  cent,  watery  solution  of  common 
salt,  these  corpuscles  can  often  be  separated  from  the  bundles, 
and  then  they  will  be  seen  to  form  a  connected  system.  When 
entirely  isolated  from  one  another,  they  often  appear  spindle- 
shaped.  That  this  is  not  their  character  may  be  shown  by 
passing  a  current  of  fluid  through  the  specimen — a  method 
already  described  under  the  name  of  irrigation.  It  is  accom- 
plished in  this  way  :  having  affixed  small  strips  of  filter-paper 
to  the  edges  of  the  cover  on  either  side,  and  moistened  one  side 
with  fluid,  the  excess  will  be  absorbed  by  the  other  slip,  caus- 
ing a  current  by  which  the  corpuscles  may  be  made  to  roll 
over.  We  then  learn  that  they  are  disks  of  an  irregularly 
flattened  form,  having  longer  or  shorter  processes  (c,  c,  Fig. 
25) — variations  in  form  which  seem  to  depend,  in  a  great 
measure,  upon  the  tension  to  which  they  are  exposed,  and  the 
position  they  occupy  in  the  tissue.  This  explanation  will 
serve  to  show  why  all  measurements  of  such  corpuscles  are 
merely  approximative,  and  have  but  little  value. 

They  are  shrunken  by  immersion  in  alcohol,  swollen  by  the 
imbibition  of  water,  are  drawn  out  into  long,  flattened  spindles 
when  the  tissue  is  put  on  the  stretch,  or  become  rounded,  per- 
haps nearly  spherical,  during  relaxation.  They  may  assume 
almost  any  form  as  the  result  of  pressure. 

The  nucleus  may  be  regarded  as  more  of  an  exception  to 
this  rule ;  at  any  rate  it  seems  that  in  fresh  specimens,  when 
the  substance  has  been  swollen  by  immersion  in  water,  it  is 
always  oval  and  flattened. 

The  bundles  upon  which  these  bodies  lie  are  somewhat 
cylindrical  in  form,  branched,  and  composed  of  separate  fila- 
ments, that  can  be  separated  by  Mueller's  fluid,  or  a  10  per 
cent,  wate^  solution  of  common  salt. 

Two  other  forms  of  corpuscles  may  also  be  noticed :  (1)  the 
kind  observed  by  Waldeyer,  and  called  plasma  cells,  and 
thought  by  him  to  be  corpuscles  peculiarly  prone  to  take  up 
fat  to  make  fat  tissue,  bodies  four  or  five  times  the  size  of 
a  lymphoid  corpuscle,  and  rounded  in  form,  containing  a  cen- 
tral body  ;  and  (2)  the  ordinary  lymphoid  corpuscles,  seen  at 
times  in  all  tissues. 


G8 


MANUAL    OF    HISTOLOGY. 


The  form  of  fibrous  tissue  that  occurs  in  parallel  lamellae  is 
well  shown  in  the  mesentery  of  the  frog,  and  in  serous  mem 
branes  generally.  No  great  difficulty  will  be  met  with  in  pre- 
paring this  tissue,  for  it  is  only  necessary  to  remove  it  from  the 
frog  in  the  fresh  state,  acidulate  it  in  a  weak  (1  per  cent.) 
watery  solution  of  acetic  acid,  and  mount  it  in  glycerine. 

It  will  be  seen  that  these  so-called  spindle-cells  are  really 
flattened  plates,  when  viewed  flat-wise,  and  generally  irregu- 
larly quadrilateral,  though  the  form  varies  somewhat  in  each 
instance. 

It  is  not  improbable  that  some  which  appear  spindle-shaped, 
and  lie  in  the  interfascicular  spaces,  have  a  double  office,  one 
of  which  is  to  guard  the  nutrition  of  the  tissue,  and  the  other 
to  form  a  partial  lining  of  a  lymphatic  channel.  The  researches 


FIG.  26. — Connective  tissue  in  the  mesentery  of  the  frog. 

of  Klein  tend  to  establish  this  double  relation,  for  they  show 
that  these  corpuscles  lie  in  the  walls  of  the  tymphatic  radicles, 
which  are  themselves  in  direct  communication  with  the  perito- 
neal cavity  by  breaks  in  the  endothelial  connective-tissue  cor- 
puscle coating  and  in  actual  apposition  with  the  endothelial 
elements  of  the  serous  membranes. 

During  the  last  few  years  there  has  been  a  tendency  to  regard  the  serous 
membranes,  especially  such  as  have  large  openings  and  slight  reticula,  as 
having  no  connective-tissue  corpuscles,  other  than  the  endothelial,  which  form, 


THE    CONNECTIVE    SUBSTANCE    GliOUP.  GO 

a  covering  over  them.  In  the  larger  trabecles,  however,  there  are  connec- 
tive-tissue corpuscles,  in  addition  to  those  just  mentioned;  they  are  well 
seen  in  profile,  interposed  between  the  bundles  (Fig.  26). 

Adenoid  tissue  (Fig.  27). — Adenoid  tissue  is  the  name  given 
to  the  delicate  substance  that  forms  the  framework  of  the  lym 
phatic  glands.  It  consists  of  fibres  in  networks  which  form  an 


FIG.  27.— Adenoid  tissue  from  a  human  lymphatic  gland. 

intricate  texture,  that  is  filled  with  the  rounded  bodies  com- 
monly known  as  lymphoid  cells.  It  is  exceedingly  difficult  to 
analyze  these  tissues,  because  it  is  not  easy  to  demonstrate  any- 
thing that  conveys  to  the  eye  our  idea  of  a  cell,  i.  e.,  excepting, 
of  course,  the  lymphoid  corpuscle.  The  best  mode  of  proced- 
ure is  the  following :  Take  a  lymphatic  gland — such  as  the  in- 
guinal in  the  early  stage  of  inflammation :  harden  at  first,  in 
Mueller's  fluid,  and  then  in  alcohol,  and  make  sections  through 
it. 

On  viewing  such  a  specimen  under  the  microscope  it  will 
exhibit  a  delicate  meshwork,  packed  with  lymphoid  corpuscles 
(Fig.  27,  a).  Now,  if  we  take  such  a  section  and  agitate  it  in  a 
test-tube  with  water  for  a  considerable  length  of  time,  and  then 
place  it  upon  a  glass  slide,  pencilling  it  with  a  camel' s-hair 


70  MANUAL    OF    HISTOLOGY. 

brush,  most  of  the  lymphoid  cells  will  be  removed,  and  the 
delicate  network,  c,  will  be  very  thoroughly  exposed. 

It  will  be  seen  that,  at  certain  parts  of  this  mesh  work,  there 
are  flattened  bodies,  b,  of  small  size,  lying  upon  the  larger 
cords  of  the  meshes.  It  has  been  held  by  Klein  and  other  his- 
tologists  that  the  reticulum  is  made  of  branching  corpuscles  ; 
but  this  statement  must  be  modified.  In  some  instances  the 
appearance  of  netted  corpuscles  is  well  seen  in  those  portions 
of  the  glands  that  are  regarded  as  the  lymph  passages,  where 
the  adenoid  tissue  forms  the  framework  of  the  part.  The  net- 
work seems  to  be  comprised  of  delicate,  silk-like  cords,  enclos- 
ing vast  numbers  of  lymphoid  corpuscles,  and  exhibiting,  at 
the  nodal  points  of  the  meshes,  flattened  corpuscles.  These 
delicate  fibres,  however,  are  often  replaced  by  heavy  trabecles, 
<?,  such  as  are  seen  in  the  figure,  and  after  continual  inflamma- 
tions the  diameter  of  these  latter  may  be  found  greater  than 
that  of  the  spaces. 

In  these  latter  instances  it  is  often  difficult  to  find  any  cor- 
puscular elements  that  may  not  be  separated  from  the  fibres  ; 
and,  indeed,  large  areas  of  these  fibrous  networks  may,  by  dil- 
igent pencilling  with  a  camel' s-hair  brush,  be  swept  clean  of 
corpuscles.  But  neither  this  rough  method,  nor  agitation  in  a 
test-tube,  will  always  succeed  in  separating  all  the  corpuscles 
from  the  fibres,  even  after  an  immersion  in  common  salt  solu- 
tion for  many  weeks.  The  sum  of  the  whole  matter  is,  that 
adenoid  tissue  does  not  generally  consist  of  a  network  of 
branching  corpuscles,  as  has  been  claimed,  but  rather  of  a  net- 
work of  fibrous  cords,  on  which  the  corpuscles  are  superim- 
posed ;  they  may  anastomose,  but  this  point  seems  difficult  to 
demonstrate  in  most  cases. 

Possibly  higher  powers  than  those  now  in  use,  or  some  new 
method  may  solve  the  question.  Where  the  fibrous  networks 
have  attained  some  thickness,  there  is  no  doubt  that  we  find 
the  ordinary  flattened  connective-tissue  plates  lying  on  the 
bundles  and  surrounded  by  a  delicate  envelope. 

Neuroglia  (Fig.  28). — But  a  short  time  since  it  was  not 
known  positively  whether  the  delicate,  supporting  substance  of 
the  nervous  system,  especially  of  the  brain,  was  granular  or 
fibrous.  Even  after  Virchow  insisted  that  this  substance  was 
like  the  other  tissues,  known  as  connective,  doubt  was  thrown 
upon  the  matter,  for  the  defining  power  of  most  objectives  then 


THE    CONNECTIVE    SUBSTANCE    GEOUP. 


71 


used  was  insufficient  to  make  out  such  delicate  objects.  At 
the  present  time  the  actual  existence  of  a  network  is  hardly 
called  in  question,  for  it  may  be  demonstrated  with  really  good 
glasses,  such  as  some  of  the  immersion  lenses  (No.  10)  of  Hart- 
nack's  system,  and,  indeed,  by  other  lenses  made  both  at  home 
and  abroad.  As  to  the  question  of  the  corpuscular  elements 
there  is  more  doubt,  and  it  can  hardly  be  said  that  their  exact 
form  and  shape  have  been  definitely  agreed  upon  by  histolo- 
gists.  We  lind,  it  is  true,  that  where  there  is  a  considerable 
deposit  of  connective  mate- 
rial along  the  central  canal  of 
the  spinal  cord,  we  have  the 
ordinarjr  fibres  and  corpuscles 
already  described,  and  so,  too, 
near  the  surface  of  the  con- 
volutions. When,  however, 
we  examine  the  supporting 
substances  of  the  white  and 
gray  masses  there  is  less  cer- 
tainty. The  actual  condition 
may  be  tolerably  well  seen 
by  adopting  the  following 
plan.  Place  any  portion  of 
the  brain  or  cord  a  few  days 
in  a  weak  solution  of  bichro- 
mate of  potash  (5  per  cent.) 

or  Mueller' s  fluid,  then  immerse  it  in  alcohol  until  hard  ;  make 
thin  sections  and  stain  for  twenty -four  hours  with  the  follow- 
ing solution  of  hsematoxylin  :  hsernatoxylini,  gr.  lij.  ;  aluminis, 
1  j.  ;  aquse,  ?  viij.  ;  mix  arid  strain. 

Wash  in  distilled  water  and  mount  in  glycerine,  tease  with 
needles  and  examine  with  a  high  power ;  there  will  then  be 
little  difficulty  in  seeing  that  the  delicate  supporting  substance 
of  both  gray  and  white  matter  consists  of  fibres.  They  may 
even  be  distinctly  isolated,  for  the  coloring  matter  darkens  them 
somewhat  and  they  become  hardened  at  the  same  time  so  as  to 
be  somewhat  stiff  and  unyielding.  It  will  be  seen  that  many 
fibrils  are  disposed  in  parallel  rows  which  perhaps  can  hardly 
be  called  bundles,  but  rather  thin  laminae ;  other  similar  fibrils 
cross  them  at  various  angles,  giving  to  the  whole,  with  a 
moderately  high  power,  the  appearance  of  a  very  delicate 


FIG.  28. — Human  brain  showing  neuroglia. 


72  MANUAL    OF    HISTOLOGY. 

meshwork,  a.  It  does  not  appear  as  if  the  fibrillse  anastomose 
with  one  another,  though  this  point  cannot  now  be  definitely 
settled.  It  must  be  stated  that  some  of  these  fibrils  are  possi- 
bly nerve-elements,  and  yet  this  is  doubtful,  because  they  do 
not  even  seem  to  be  connected  with  the  nerve-fibres '  that  are 
distinctly  shown  by  this  method  of  preparation. 

Granular  appearances  are  always  noted  in  the  brain,  which 
is  to  be  expected  when  cross-sections  are  made  of  the  delicate 
fibrillse.  Three  kinds  of  corpuscles  are  met  with  in  the  brain 
and  medulla.  The  first  are  the  variously  shaped  ganglionic 
corpuscles  or  cells,  Fig.  28,  &,  b,  b  ;  secondly,  the  ordinary 
lymphoid  cells,  c,  c,  which  are  generally  seen  to  have  a  pale 
envelope  about  them  ;  lastly,  smaller  corpuscles,  d,  d,  of  irre- 
gular sJiapes,  and  many  of  them  undoubtedly  flattened  and 
appearing  to  have  branching  processes.  They  may  be  found 
in  considerable  numbers,  and  can  be  isolated  so  that  there  is  no 
doubt  that  they  exist. 

The  fibrillse  of  the  neuroglia  do  not  differ  substantially  in 
size  from  the  fibrillse  of  fibrous  tissues  elsewhere. 

Tendon-tissue  (Fig.  29). — Tendon-tissue  may  be  well  studied 

in  the  gastrocnemius  of  the 
frog.  It  is  prepared  like 
the  preceding.  If,  how- 
ever, it  is  desirable  to  show 
the  nuclei  in  adult  tissue, 
it  is  well  to  use  nitrate  of 
silver.  Cut  a  thin  section 
of  a  fresh  tendon  and  ex- 
pose it  for  a  few  minutes 
in  a  £  per  cent,  solution 
of  nitrate  of  silver,  until 
the  section  is  turbid  or 
milky,  then  place  in  the 
sunlight,  and  in  a  few  min- 

F^.-Tenaon.tl^fco.nthe^.  ^    ^    ^^  ^^   ^ 

give  place  to  dark  brown  or  black,  owing  to  the  deposit  of 
silver,  and  the  tissue  may  then  be  mounted  in  glycerine  and 
examined. 

This  method  will  show  the  corpuscular  bodies  to  advantage. 

1  To  avoid  confusion  they  are  not  represented  in  the  drawing. 


THE    CONNECTIVE    SUBSTANCE    GROUP.  73 

In  some  cases  better  results  are  obtained  by  the  use  of  chloride 
of  gold.  The  method  is  as  follows :  Freeze  a  small  portion  of 
a  tendon,  then  make  the  thinnest  possible  section,  acidulate  it 
slightly  and  immerse  in  a  j-  per  cent,  solution  of  chloride  of 
gold  until  a  strong  yellow  color  has  been  obtained,  then  soak  in 
a  J  per  cent,  solution  of  dilute  acetic  acid  and  expose  to  the 
sunlight  until  a  purple  or  reddish  color  has  been  obtained. 
This  will  take  a  variable  time,  and  is  not  always  successful,  for 
reasons  which  are  not  easy  to  understand. 

At  considerable  distances  from  one  another  there  will  be 
seen  small  dark  bodies,  which  are  the  corpuscles  already  de- 
scribed. It  is  difficult  to  determine  whether  or  not  these  cor- 
puscles are  connected  together.  To  isolate  them,  take  a  small 
piece  of  young  tendon- tissue,  immerse  three  or  four  days  in  a 
10  per  cent,  solution  of  common  salt,  and  then  tease.  In  this 
way  the  cells  may  be  liberated,  and  they  will  prove  to  be  irre- 
gularly flattened  plates. 

Sometimes  they  lie  at  the  intersection  of  several  bundles 
and  then  have  separate  expansions  for  each  bundle  ;  the  plates 
then  lie  at  various  angles  with  one  another,  and  if  one  be  seen 
edgewise  it  looks  as  if  the  corpuscle  proper  were  traversed  by 
a  line. 

Silver  or  gold,  the  latter  especially,  is  generally  necessary 
to  show  the  corpuscles  in  old  tendons.  The  same  method 
shows  the  fibrillated  tissue  to  advantage.  The  large  tendon 
bundles  are  often  covered  with  endothelium  (connective- tissue 
corpuscles),  which  are  continuous  and  form  a  complete  invest- 
ment. 

For  the  smaller  bundles  the  tendon- corpuscles  do  not  by 
any  means  form  a  connected  sheath.  In  very  young  tendons 
they  are  quite  near  to  one  another,  though  even  at  this  time 
they  only  form  a  partial  investment  for  the  bundles  ;  but  as 
the  tendon  grows  older  the  corpuscles  become  smaller,  with- 
draw from  one  another,  and  sometimes  almost  disappear. 

Tendon  bundles,  like  other  forms  of  connective  tissue,  are 
often  encased  in  a  transparent,  delicate  membrane,  not  unlike 
the  sarcolemma  of  striped  muscular  tissue.  It  is  well  shown 
by  immersing  the  tendon  in  a  dilute  solution  of  acetic  acid. 

Fat  tissue. — The  ordinary  fibrillated  connective  tissue  often 
becomes  the  deposit  for  oil,  which  fills  the  corpuscles,  making 
them  swell  out  enormously.  This  is  fat  tissue.  An  excellent 


74  MANUAL    OF    HISTOLOGY. 

way  of  showing  it  consists  in  making  a  section  through  fat  tis- 
sue that  has  been  hardened  in  alcohol  or  Mueller's  fluid,  or  both. 
The  phenomena  will,  in  this  way,  be  well  shown.  After  im- 
mersion in  an  acid  solution,  it  will  be  seen  that  the  fatty  acids 
crystallize  in  the  centre  of  the  sac. 

The  nature  of  the  evidence  that  fat  corpuscles  are  really  the 
altered  corpuscles  of  the  fibrous  tissues  is  as  follows :  They 
occupy  the  same  position,  being  in  rows,  between  the  bundles, 
just  as  the  other  corpuscles  that  we  have  mentioned  ;  a  few  oil 
drops  at  first  appear,  then  others,  until  finally  they  coalesce 
into  a  single  large  drop,  which  fills  the  corpuscle  ;  if  fat  tissue 
be  pressed,  and  the  oil  escapes,  the  walls  of  the  fat-corpuscles 
collapse,  and  then  the  flattened  nuclei  may  be  observed  on  the 
side  of  the  cell-body. 

Waldeyer  believes  that  there  is  a  peculiar  corpuscle,  three 
to  five  times  the  size  of  the  lymphoid,  and  roundish,  which  is 
especially  prone  to  take  up  fat,  and  be  converted  into  a  fat- 
corpuscle. 

This  body,  known  as  the  plasma  cell,  is  the  second  element 
that  forms  the  fat -cell.  The  change  is  said  to  occur  only  occa- 
sionally, and  under  favorable  conditions  of  alimentation 
(Klein). 

The  same  author  states  that  there  is  also  a  third  way  in 
which  fat  is  formed  :  In  many  parts  of  serous  membranes,  espe- 
cially in  connection  with  the  large  vessels,  there  appear  "  no- 
dules or  cords,  which  are  made  up  of  multiplying  connective- 
tissue  cells."  The  cells  increase,  the  matrix  is  converted  into  a 
network,  lymph-corpuscles  appear,  the  tissue  is  supplied  with 
arteries,  veins,  and  capillaries,  and  resembles  lymphatic  tissue. 
Sometimes  these  structures  persist  as  they  are  ;  in  other  cases 
they  are  converted  into  fat -tissue. 

Eanvier  recommends  the  following  plan  of  demonstrating 
fat-tissue  :  He  injects  beneath  the  skin  a  weak  solution  of  os- 
mic  acid  (1-1000),  The  connective-tissue  corpuscles  may  be 
seen  to  be  more  or  less  filled  with  oil-globules. 

•  The  property  of  taking  up  oil  is  not  peculiar  to  these  cor- 
puscles already  described,  but  belongs,  physiologically,  to  the 
liver,  to  adult  cartilage,  the  glandular  elements  of  the  female 
breast  during  lactation,  and  the  glandular  epithelium  of  the 
sebaceous  glands. 

Inter  muscular  tissue. — It  has  been  claimed  by  some  that 


THE    CONNECTIVE    SUBSTANCE    GKOUP.  75 

there  is  a  form  of  spindle-cell  in  the  interamscular  tissue  of  the 
frog's  thigh.  This,  however,  is  apparent  rather  than  real.  We 
find  broad  plates,  in  which  are  oval,  flattened  bodies,  placed  at 
certain  distances  apart  (Fig.  31).  These,  seen  in  profile,  appear 
spindle-shaped.  There  is  something  peculiar  about  such 
bodies,  for  they  seem  to  bear  a  close  relationship  to  the  elastic 
networks,  a,  so  that,  in  some  cases,  it  appears  as  if  the  flat- 
tened central  bodies  were  directly  connected  with  the  elastic 
fibres,  as  stated  by  Boll. 

In  many  instances  these  elastic  fibres  lie  upon  the  plates,  &, 
which  themselves  rest  in  a  homogeneous,  intermediate,  and 
apparently  structureless  substance. 

This  tissue  is  therefore  similar,  in  some  respects,  to  mucous 
tissue. 

Corneal  tissue. — The  cornea  consists  of  thin,  fibrous  bands, 
each  one  partly  anastomosing  with  its  adjacent  neighbor. 
Between  them  are  well-marked  corpuscles  lying  in  clefts — the 
corneal  spaces. 

The  term  cornea!  corpuscles,  however,  is  even  now  applied 
to  the  spaces  by  some  of  the  best-known  writers,  and  it  seems 
evident  that  there  is  doubt  as  to  whether  real  corpuscles  exist 
or  not.  Recently  the  subject  has  been  restudted  by  Waldeyer, 
and  the  author  has  been  able  to  verify  his  conclusions  in  a 
great  measure,  both  as  to  the  character  of  the  corpuscles  and 
the  spaces  in  which  they  lie. 

In  general,  these  bodies  appear,  as  stated  by  Waldeyer,  to 
be  fiat,  having  a  considerable  amount  of  protoplasmic  material 
about  their  nuclei  (Fig.  30),  though  in  the  direction  6f  the  per- 
iphery they  gradually  caper  off  into  thin  expansions,  which  are 
nearly  homogeneous,  and  extending  from  them  are  distinct 
processes  which  in  part  unite  with  those  of  other  corpuscles, 
not  materially  differing  in  this  respect  from  tendon-tissue  and 
the  other  varieties.  In  them  is  the  same  flattened,  oval  body, 
which,  when  seen  on  the  side,  is  rod-shaped,  5,  and  is  sur- 
rounded by  an  irregular  envelope  that  assumes  almost  any 
shape.  Thus  the  corpuscles  are  not  always  flat,  though  they 
are  usually  so.  Their  shape  depends  upon  many  different 
causes,  such  as  the  method  of  preparing  the  tissue,  the  amount 
of  laceration  to  which  it  is  subjected,  etc.  The  best  method  6t' 
examining  the  cornea  consists  in  preparing  it  by  the  gold  me- 
thod, already  described. 


76 


MANUAL    OF    HISTOLOGY. 


After  the  tissue  has  been  properly  stained,  which  is  known 
when  it  has  taken  a  mauve  or  violet  tint,  as  already  stated,  the 
specimen  should  be  allowed  to  stand  in  the  sun.  Thin  lamel- 
lae are  then  torn  off  with  the  forceps  and  mounted  in  dammar 
varnish  or  Canada  balsam. 

After  the  specimen  has  been  made  thoroughly  transparent 
by  soaking  in  oil  of  cloves,  it  will  then  be  seen  that  there  are 
bodies  within  certain  well-defined  areas — the  corneal  spaces, 


FIG.  30.— Corneal  tissue.     From  the  rabbit. 

as  they  have  been  called  by  Recklinghausen  and  others.  These 
bodies  are  disposed  at  quite  regular  intervals  throughout  the 
cornea,  and  are  generally  flat  with  rounded  contours,  though 
often  they  have  processes  extending  from  them  in  various  direc- 
tions. In  the  accompanying  drawing  the  spaces  may  be  dis- 
tinctly seen,  as  well  as  the  variously  shaped  corneal  corpuscles. 
One,  c,  is  crowded  into  the  prolongation  of  a  corneal  space, 
while  another,  5,  is  connected  by  its  processes  with  a  neighbor- 
ing corpuscle.  One  corneal  space,  a,  is  entirely  empty.  These 
differing  conditions  are  in  a  measure  due,  probably,  to  the 


THE    CONNECTIVE    SUBSTANCE    GROUP.  77 

laceration  of  the  tissue  in  preparing  it,  some  of  the  bodies 
having  been  torn  out  and  others  forced  to  the  side  of  the  cor- 
neal  space.  There  seems  to  be  a  very  general  agreement  that 
the  intercellular  substance  may  be  separated  into  indepen- 
dent fibrils  ;  but  I  have  seen  no  decisive  proof  bearing  on  this 
point. 

Elastic  tissue. — This  differs  from  the  other  forms  micro- 
scopically and  chemically,  though  it  is  often  combined  with 
them  in  the  body.  It  is  also  convenient  to  class  it  by  itself 
for  other  reasons,  chief  of  which  are,  that  its  corpuscular  ele- 
ments have  not  yet  been  definitely  shown  in  adult  tissue. 
Virchow,  some  years  ago,  stated  that  this  tissue,  as  well  as 
other  connective  substances,  was  composed  of  networks,  the 
substance  of  the  fibres  containing  certain  markings,  and  he  in- 
ferred that  these  latter  might  be  the  corpuscles  of  the  tissue. 
Elastic  fibres  were,  however,  according  to  him  and  others,  noth- 
ing but  the  ordinary  fibrous  tissue  condensed.  Each  fibre  was 
hollow  and  capable  of  conveying  the  nutritive  juices. 

Henle,  in  his  earlier  writings,  regarded  the  elastic  fibres  as 
emanating  from  the  nuclei,  of  which,  in  fact,  he  stated  they 
were  prolongations.  Subsequently,  he  seems  to  have  believed 
that  the  fibres  originated  in  the  basis  substance. 

Reichert  could  not  trace  the  connection  between  the  nuclei 
and  the  elastic  fibres,  and,  when  the  latter  had  formed,  the 
former  had  disappeared. 

Boll,  however,  distinctly  stated  that  the  elastic  fibres,  each 
one  constituting  an  "elastic  cord,"  arise  from  the  plate-like 
cells. 

Ranvier  examined  tendon-tissue,  as  mentioned  before,  but 
he  was  only  able  to  find  the  elastic  fibres  after  boiling  the  tis- 
sue from  eight  to  ten  hours.  It  is  proper,  however,  to  add 
here,  that  elastic  fibres  are  very  uncommon  in  tendon- tissue, 
at  least'  they  have  not  often  been  observed. 

The  fibres  of  the  elastic  substance  are  pretty  readily  re- 
cognized by  the  fact  that  they  are  not  colored  by  carmine  or 
hsematoxylin,  and  do  not  swell  with  acetic  acid  ;  they  branch 
dichotomousty,  these  branches  forming,  with  similar  branches 
of  other  elastic  fibres,  networks. 

Elastic  tissue  prevails  in  the  ligamentum  nuchse  of  the  ox, 
in  the  serous  membranes  generally,  and  in  the  subcutaneous 
connective  tissue  of  the  skin,  as  well  as  in  the  delicate  inter- 


78 


MANUAL    OF    HISTOLOGY. 


muscular  substance  already  described.  It  will  generally  be 
found  that  where  this  material  occurs  in  bundles  it  is  not  be- 
cause there  are  no  meshes,  but  rather  because  they  are  com- 
pressed laterally,  so  as  not  to  be  apparent  unless  most  carefully 
teased  apart.  When  such  fibres  are  broken  off,  their  extremi- 
ties curl  up  ;  further,  the  fibres  are  unaffected  by  being  boiled 
in  solutions  of  strong  acids  and  alkalies,  such  as  35  per  cent. 


FIG.  31.— Elastic  tissue  networks.     From  the  frog. 

solutions  of  caustic  potash,  or  nitric  acid  (standard  prepara- 
tions commonly  used  in  laboratories),  unless  the  action  is  pro- 
longed for  a  considerable  time.  These  networks  are  beautifully 
shown  by  taking  the  mesentery  of  the  frog  when  slightly  con- 
tracted after  immersion  in  acetic  acid.  The  fibrillated  connec- 
tive tissue  will  then  swell  up  and  become  invisible,  while  the 
elastic  fibres  are  unaffected. 

The  ligamentum  nuchse  also  affords  an  excellent  oppor- 
tunity for  studying  this  tissue  by  itself.  To  render  the  work 
more  easy,  the  specimen  may  be  allowecj.  to  soak  a  few  days  in 
a  10  per  cent,  watery  solution  of  common  salt,  so  that  it  may 
be  the  more  easily  teased.  In  the  subcutaneous  connective 
tissue  of  the  skin  the  elastic  fibres  are  well  shown  by  hferna- 
toxylin  preparations.  Being  unaffected  by  this  staining  solu- 
tion they  appear  as  bright,  silk-like  cords,  which  lie  in  close 
apposition  with  the  wavy  bundles,  and  the  branches  arch  over 
the  bundles,  to  anastomose  with  corresponding  branches  of 
other  bundles,  so  that  in  this  way  meshes  are  formed.  Some 
writers  have  spoken  of  little  knobs  at  the  nodal  points  of  the 
meshes,  but  these  appearances  have  been  illusory. 

Recklinghausen  seems  to  have  believed  with  Virchow,  that 
the  elastic  fibres  contain  peculiar  nuclei  of  their  own,  which  in 


THE    CONNECTIVE    SUBSTANCE    GEOUP.  79 

adult  tissue  become  extremely  small,  and  are  represented  by 
the  dark  markings  seen  in  them.  Thin,  of  London,  has  claimed 
that  they  originate  in  branching  corpuscles,  which  by  their 
coalescence  form  the  network,  and  the  remains  of  the  nucleus 
may  be  shown  by  hsematoxylin.  These  markings  may,  it  is 
true,  be  seen  in  the  ligamentum  nuchse  of  the  ox,  but  it  is 
doubtful  whether  they  are  nuclei  or  mere  clefts  in  the  tissue. 
Examination  by  the  author,  with  such  high  powers  as  Gund- 
lach'  s  No.  15  immersion,  and  Wale' s  TV,  have  failed  to  clear 
up  the  matter. 

Good  examples  of  human  elastic  tissue  are  found  in  the 
sloughs  of  ulcers  and  in  the  sputa  of  phthisical  patients. 

In  some  portions  of  the  body  these  networks  are  stouter, 
as  in  the  bronchi  and  trachea  ;  here  they  almost  form  a  layer 
by  themselves  ;  some  of  the  fibres  are  even  said  to  have  a 
sheath. 

There  is  a  variety  that  has  been  called,  by  Henle,  perforated 
membrane.  It  is  found  in  arteries  and  veins.  The  fibres  are 
broad  and  the  meshes  very  small.  There  are  also  "  continuous 
elastic  membranes."  They  are  made  up  of  fibrils,  react  chemi- 
cally like  elastic  tissue,  and  have  no  meshes.  Such  is  Bow- 
man'  s  elastic  membrane  in  the  human  cornea,  which  is  very 
distinct  in  man,  also  Descemet's  membrane — the  posterior 
elastic  membrane  of  the  cornea. 

In  various  parts  of  the  body,  beneath  the  epithelium,  there 
are  other  elastic  membranes  which  will  be  noticed  in  their 
proper  places.  The  elastic  membrane,  made  of  endothelium, 
and  forming  the  basement  membrane  of  gland-ducts,  must  not 
be  confounded  with  those  first  described. 

The  growth  and  development  of  connective  tissue  varies  ac- 
cording to  the  particular  type.  It  is  probable,  however,  that 
all  the  corpuscles  are  first  round,  but  soon  become  flattened 
and  have  a  delicate  envelope  (Fig.  32,  &). 

About  this  is  a  further  lightly  attached  investment,  which, 
uniting  with  those  of  other  similar  bodies,  is  the  commence- 
ment of  the  intercellular  substance.  At  first  the  plate-like 
bodies  lie  in  niches,  as  it  were,  in  the  intercellular  substances, 
and  if  one  is  brushed  out  it  leaves  a  socket  behind  it  (Fig.  32,  c). 
They  are  often  arranged  in  rows,  as  in  the  drawing,  which  was 
taken  from  a  fibroma  of  the  scalp.  As  the  intercellular  sub- 
stance increases  the  corpuscles  become  smaller,  while  imme- 


80 


MANUAL    OF    HISTOLOGY. 


diately  under  them  thin  laminae  are  formed,  probably  from 
the  effused  fibrine — the  commencement  of  fibrillation. 

As  the  corpuscles  become  smaller  their  envelope  shrinks, 
and  they  recede  from  one  another.  Yet,  in  many  cases,  they 
may  retain  connection  with  one  another  by  means  of  their  pro- 

cesses.  In  advanced  life  these  cor- 
puscles  are  generally  more  or  less 
flattened,  but  their  form  is  also  con- 
siderably  modified  by  the  age  of  the 
tissues  and  various  mechanical  alter- 
ations  to  which  they  are  subjected, 
according  to  the  particular  locality 
in  which  they  occur  or  the  province 
they  have  to  fill. 

By  referring  to  Fig.  32  it  will  be 
seen  that  the  delicate  protoplasm,  Z>, 
has  processes  which  corne  clearly  in- 
to view  where  the  corpuscles  are  iso- 
lated. 

Pavement  endotJielium  (epitheli- 
um).— From  the  views  that  have  been 
advanced  it  is  plain  that  we  are  pre- 
pared to  abandon  the  old  idea  that  the 
mesentery,  peritoneum,  the  pleura, 
endocardium,  serous  cavities,  and  ten- 
Fl(^  32— Development  of  fibrous  tis-  dinous  sheaths  are  lined  with  epithe- 

sue.    Fibroma  of  the  scalp.  r 

lium.    It  is  becoming  more  and  more 

evident  from  studies  in  the  lymphatics  that  they  are  lined  with 
connective-tissue  corpuscles,  which,  on  the  one  hand,  are  in 
actual  continuity  with  the  interfascicular  connective-tissue  cor- 
puscles, and,  on  the  other,  with  the  pavement  corpuscles  of 
the  serous  cavities.  It  is  but  a  step  farther  and  in  the  same 
direction  to  trace  the  endothelium  of  the  endocardium  out 
through  the  arteries  and  veins  into  the  capillaries  and  recog- 
nize the  connective-tissue  corpuscle  as  the  one  cellular  element 
of  all  these  tissues.  The  special  methods  by  which  these  parts 
are  studied  may  be  found  described  in  the  chapters  more  es- 
pecially devoted  to  these  topics.  Nitrate  of  silver  and  chloride 
of  gold  are  still  prominent  among  the  reagents  that  demon- 
strate them  most  distinctly. 

Ehrlich  has  recently  described  peculiar  connective-tissue 


BIBLIOGRAPHY.  81 

corpuscles,  which  he  previously  supposed  to  be  identical  with 
Waldeyer'  s  plasma  cells,  but  which  he  is  now  inclined  to  re- 
gard as  a  distinctive  group  of  bodies.  They  are  characterized 
by  a  special  power  of  intense  coloration  in  specimens  treated 
with  certain  of  the  aniline  dyes.  Red  and  violet  colors  appear 
to  be  best  suited  to  reveal  the  presence  of  these  bodies,  called 
by  Ehrlich  granular  cells.  Acetic  acid  produces  a  diffuse 
staining  of  the  nucleus  in  these  aniline  stained  cells.  At  the 
same  time  the  conspicuous  granules  lose  their  color.  The  same 
author  also  states  that  the  granular  cells  commonly  found  in 
such  great  abundance  in  inflammatory  processes  are  not  modi- 
fied leucocytes,  but  are  derived  from  the  fixed  connective- 
tissue  corpuscles. 

According  to  Ravogli,  the  connective-tissue  corpuscles  of 
the  corium  and  subcutaneous  tissue  are  branching  cells,  whose 
processes  unite  to  form  anastomoses.  With  advancing  age  these 
cells  undergo  structural  alterations,  and  their  processes  begin 
to  form  reticula  of  elastic  tissue.  Simultaneously  with  this 
metamorphosis  the  cell-bodies  are  said  to  become  flattened, 
elongated,  and  united  in  longitudinal  rows.  At  length  the  cells 
as  well  as  their  processes  are  transformed  into  ordinary  elastic 
tissue. 


BIBLIOGRAPHY. 

SATTERTHWAITE,  T.  E.  On  the  Structure  and  Development  of  Connective  Sub- 
stances (Prize  Essay).  New  York  Med.  Jour. ,  July,  1876,  and  Monthly  Micro- 
scop.  Jour.,  October  and  November,  1876. 

FLEMMING.     Arch.  f.  Anat.,  etc.     1879.     401—454. 

STRICKER.    Allg.  Wien.  med.  Ztg.     1879.    XXIV.,  547. 

KOLLMANN.     Centralbl.  f.  d.  med.  Wiss.     1878.     XVI.,  881. 

EHKLICH.  Verhandl.  d.  Berliner  phys  GeselL  Jan.  17,  1879;  Arch.  f.  Anat.  u. 
Phys.  Phys.  Abtheil.  pp.  166—169.  1879. 

RAVOGLI.     Wien.  med.  Jahrb.  Heft  1,  p.  49.     1879. 
Also  the  more  recent  text-books  of  Klein  and  Eanvier. 

6 


CHAPTER  VI. 

THE  CONNECTIVE  SUBSTANCE  GKOUP—  Continued. 
CARTILAGE. 

CARTILAGE  is  divided  into  three  prominent  varieties :  1, 
hyaline ;  2,  fibrous ;  and  3,  elastic  or  yellow.  There  is,  in 
addition,  a  form  called  ossifying,  which  will  be  described  in 
connection  with  the  development  of  bone. 

Hyaline  cartilage  is  the  tissue  from  which  the  bones  of  the 
skeleton  are  first  made ;  it  is  also  found  in  the  articular  and 
costal  cartilages,  and  in  the  cartilages  of  the  larynx,  trachea, 
and  bronchi ;  possibly  also  in  some  of  the  nasal  cartilages,  and 
in  portions  of  the  sternum.  All  of  these  tissues  consist  of  a 
solid  material  or  matrix,  in  which  are  capsules  which  contain 
the  true  cartilage  corpuscles. 

The  character  of  the  intercellular  substance  determines  the 
particular  variety.  Thus,  hyaline  cartilage  appears,  under  the 
microscope,  to  be  structureless  and  homogeneous.  Fibrous 
cartilage,  on  the  other  hand,  has  distinct  lines  of  fibrillation 
extending  through  it.  Elastic  cartilage  is  permeated  by  net- 
works of  elastic  fibrils. 

Hyaline  cartilage,  though  so-called  because  of  its  apparent 
absence  of  structure,  is  now  known  to  be  less  often  structure- 
less than  has  been  supposed,  for  the  researches  of  Tillmanns 
have  revealed  distinct  marks  of  fibrillation  in  some  adult  artic- 
ular and  costal  cartilages.  Soaking  the  tissue  in  a  10  per 
cent,  solution  of  common  salt  will  dissolve  out  the  cement  sub- 
stance and  isolate  fibrils,  though  the  tissue  has  previously  ap- 
peared homogeneous.  Staining  with  the  picro-carminate  of 
ammonia  (Ranvier's  formula)  will  also  demonstrate  the  fibrils. 

Each  capsule  is  probably  invested  by  a  delicate  membrane, 
which  is  thicker  in  some  instances  than  in  others.  Extending 


THE    CONNECTIVE    SUBSTANCE    GROUP.  83 

from  tliis  cavity  are  minute  canals,  which  communicate  with 
those  of  other  capsules  in  many  instances,  and  thus,  in  all 
probability,  establish  a  system  of  serous  channels  which  convey 
the  plasmatic  fluid,  i.e.,  the  lymph. 

Many  years  ago  H.  Mueller  gave  a  description  of  minute  passages  radiating 
out  from  the  cartilage  capsules.  Since  this  time  the  matter  has  been  studied 
by  numbers  of  observers,  but  opinions  have  been  divided  as  to  their  existence. 
More  recently  A.  Budge  has  detailed  a  method  by  which  he  claims  that  a 
complete  lymphatic  system  can  be  demonstrated  in  hyaline  cartilage.  Em- 
ploying a  solution  of  Berlin  blue,  he  injected  the  cartilage  of  an  epiphysis  from 
which  the  articular  lamella  had  been  cut  off.  Having  thus  opened  and  exposed 
the  substance  of  the  cartilage,  he  found  it  permeated  with  minute  blue  net- 
works that  were  in  communication  with  the  cartilage  capsules.  A  connection 
with  the  lymphatics  of  the  bone  was  also  shown. 

Nykamp,  who  prosecuted  his  investigations  about  the  same  time  (1876-77), 
verified  the  work  of  Budge,  though  his  methods  were  different.  He  experi- 
mented on  rabbits,  injecting  one  gramme  of  indigo  carmine  (in  substance) 
into  the  abdominal  cavity.  Blue  granules  appeared  in  certain  spaces,  which 
had  shown  themselves  to  be  hollow  passages  by  a  previous  soaking  in  the  neu- 
tral chromate  of  ammonia.  The  cartilage  commonly  known  as  hyaline  was 
also,  by  this  means,  shown  to  be  fibrillated. 

Round  about  every  cartilage  capsule  there  is  usually  an 
area' of  hyaline  material.  When  very  thin  sections  of  cartilage 
are  made,  these  areas  sometimes  become  visible  ;  soaking  in 
acids  is  said  also  to  bring  them  into  prominence  (Klein). 

The  amount  of  intercellular  substance  in  comparison  with 
the  capsules  varies ;  as  a  rule,  there  is  less  of  this  substance 
near  the  periphery  of  the  cartilage.  When  the  amount  is  so 
very  small  that  the  tissue  is  almost  cellular,  it  is  called  par- 
encJiymatous  cartilage  ;  this  condition  is  observed  in  all  carti- 
lages, at  an  early  stage  of  development,  and  in  some  portions 
of  the  adult  forms.  The  cartilage  corpuscles  are  rounded 
bodies,  sometimes  oval  and  sometimes  pyriform.  In  the  nor- 
mal condition  they  fill  up  the  capsule,  but  after  the  application 
of  reagents  that  shrivel,  such  as  alcohol,  they  are  withdrawn 
from  the  walls  of  the  capsules,  being  only  attached  at  a  few 
points  (perhaps  where  their  processes  extend  out  through  the 
canaliculi). 

The  cell-corpuscles  and  nuclei  are  said,  by  some  recent  ob- 
servers, to  exhibit  networks  in  their  interior  (Schleicher  and 
Flemmirig).  They  frequently  contain,  in  addition,  moving 
bodies,  which  are  often  oil-globules  of  minute  size. 


84  MANUAL    OF   HISTOLOGY. 

The  cartilage  capsules  do  not  usually  appear  to  have  any 
connection  with  one  another  when  examined  in  an  indifferent 
fluid,  though  in  the  episternal  cartilage  of  the  frog,  immedi- 
ately beneath  the  perichondrium,  a  connection  may  occasion- 
ally be  seen. 

Division  of  tlie  cartilage  corpuscle. — One  of  the  prominent 
features  seen  in  cartilage  is  the  division  of  the  cartilage  cor- 
puscle. First  we  notice  the  splitting  of  the  nucleus  ;  then  of 
the  corpuscle  itself.  When  such  a  division  has  taken  place 
the  corpuscies  are  called  daughter-cells  (Fig.  33).  As  a  next 
step  each  daughter-cell  may  divide  and  again  subdivide,  and 


PIG.  33.— Fresh  cartilage  from  the  triton.     (Rollett.) 

thus  we  have  developed  in  one  capsule  four  or  eight  cor- 
puscles. Sometimes  it  will  be  observed  in  the  same  specimen 
that  with  each  division  of  a  corpuscle,  hyaline  matter  from 
without  the  capsule  pushes  in,  and  so  from  the  original  capsule 
two  are  now  formed. 

Calcification  of  hyaline  cartilage. — Hyaline  cartilage  in 
old  age  is  infiltrated  by  a  deposit  of  the  salts  of  lime,  which, 
when  seen  under  the  microscope,  have  a  granular  appearance. 
The  deposit  occurs  first  round  about  the  cartilage  capsule 
(Ranvier). 

Nerves  and  blood-vessels  are  not  supplied  to  hyaline  car- 
tilage proper,  though  blood-vessels  which  belong  to  adjacent 
tissues  sometimes  dip  into  it  or  pass  through  it. 

Methods  of  studying  hyaline  cartilage. — An  excellent  and 
simple  plan  is  to  snip  off  the  tip  of  the  episternal  cartilage 


THE    CONNECTIVE    SUBSTANCE    GROUP.  85 

from  the  frog  ;  strip  it  of  pericliondrium  and  mount  in  serum. 
The  shoulder-girdle  of  the  triton  (newt)  may  also  be  employed. 
It  will  then  be  seen  that  there  are  numbers  of  granular  cor- 
puscles, with  nuclei  scattered  irregularly  throughout  an  ap- 
parently homogeneous,  i.e.,  structureless  matrix.  If  now  a 
little  water  be  added  to  the  preparation,  it  will  be  seen  that  the 
corpuscles  are  made  to  shrivel,  and  in  so  doing  they  expose 
the  wall  of  the  cavity  or  capsule  in  which  they  lie.  The  cor- 
puscles do  not  appear  to  have  any  uniform  size  or  shape :  some- 
times they  are  single  ;  again  they  are  double  (daughter-cells) ; 
occasionally  they  are  united  with  the  corpuscles  in  adjacent 
capsules.  The  nucleus  is  apt  to  be  round  and  full ;  the  corpus- 
cles are  apt  to  be  filled  with  dark  spherical  bodies  which  are 
usually  fatty  molecules,  as  may  be  shown  by  employing  a  di- 
lute solution  of  osmic  acid  (1  per  cent.). 

Using  the  silver  method  it  will  be  seen  that  there  exists,  in  the  apparently 
homogeneous  matrix,  numbers  of  corpuscles  whose  nature  is  not  fully  under- 
stood. Incidentally  it  may  be  mentioned  that  the  silver  method  often  exhibits 
curious  markings  in  all  tissues.  / 

Sometimes  these  appearances  are  due  to  the  silver  itself,  and  some  caution 
is  therefore  necessary  in  deducing  conclusions  from  the  method. 

The  gold  method J  shows  that  there  are  concentric  rings  about  the  capsules, 
but  it  is  highly  probable  that  this  phenomenon  is  artificial. 

Eanvier  recommends,  as  a  staining  fluid,  purpurine,  the 
formula  of  which  is  as  follows :  Take  one  gramme  of  powdered 
alum  and  add  to  it  two  hundred  grammes  of  distilled  water, 
which  boil  in  a  porcelain  dish.  To  this  solution  add  some  pow- 
dered purpurine  diluted  with  water.  If  the  boiling  be  now  con- 
tinued, a  portion  of  the  purpurine  will  dissolve.  Filter  while 
warm,  and  receive  the  colored  fluid  in  a  flask  which  contains 
60  c.c.  of  alcohol.  This  liquid  has  a  rose-orange  color.  The 
nuclei  of  the  corpuscles  will  be  colored  red  and  have  a  double 
contour  ;  the  cell-body  will  be  bright  red. 

Hyaline  cartilage  may  be  well  exhibited  in  the  respiratory 
tract  of  young  children,  as  in  the  cricoid  cartilage  of  an  infant 
two  or  three  years  old. 

Yellow  elastic  or  reticular  cartilage  is  a  very  distinctive 
form.  It  consists  of  the  hyaline  variety  permeated  with  elas- 
tic networks.  Examples  of  it  may  be  obtained  from  the  human 

1  See  chapter  on  General  Methods. 


86 


MANUAL    OF   HISTOLOGY. 


epiglottis,  laryngeal  cartilages,  and  the  pinna  of  the  ear  (Fig. 
34).  The  presence  of  elastic  fibres  is  proved  by  their  resistance 
to  boiling  in  acids  and  alkalies,  and  their  failure  to  color  with 
carmine.  Sections  may  be  made  with  the  knife  and  prepared 
in  almost  any  of  the  ways  already  mentioned. 

The  appearances  already  described  are  not  seen  in  the  early 
development  of  elastic  tissue,  but  are  easily  identified  in  adult 


FIG.  34.— Section  of  the  boiled  and  dried  auricle  of  the  human  ear  :  a,  retiform  cartilage ;    6,  connec- 
tive tissue.     (Rollett.) 

life.  Even  then  the  elastic  fibrils  may  only  be  found  in  the  in- 
terior of  the  cartilage,  while  at  the  periphery  the  matrix  is 
hyaline.  Elastic  cartilage  is  coated  over  with  a  delicate  mem- 
brane— the  pericJwndrium. 

Fibrous  cartilage. — This  variety  is  also  known  as  fibril  - 
lated  or  fibro-cartilage.  The  matrix  has  probably  no  elastic 
fibrils,  but  is  interspersed  with  connective- tissue  bundles.  It 
is  found  in  the  cartilages  which  make  the  lips  of  the  joints,  the 
inter-articular  cartilages,  the  cartilaginous  deposits  in  tendons, 
the  cartilage  of  the  symphysis  pubis  and  of  glenoid  fossae,  and 
possibly  in  the  intervertebral  ligaments  and  sesamoid  carti- 
lages. There  is  often  more  or  less  hyaline  material  about  them. 
In  many  instances  the  line  of  distinction  between  cartilage  and 
fibrous  tissue  is  difficult  to  make  out.  '  Where,  however,  dis- 
tinct corpuscles  can  be  demonstrated,  the  tissue  may  properly 
be  regarded  as  cartilage.  These  bodies  are  similar  to  those 
seen  in  hyaline  and  reticular  cartilage. 

Division  of  the  cartilage-corpuscle. — A  problem  that  has 


THE    CONNECTIVE    SUBSTANCE    GEOUP.  87 

attracted  the  study  of  various  histologists  for  a  number  of 
years,  since  Leidy,  in  1849,  first  directed  attention  to  it,  is  the 
mode  in  which  cartilage-corpuscles  divide.  Various  theories 
have  been  afloat,  each  with  its  special  supporters. 

Dr.  W.  S.  Bigelow,  of  this  country,  in  1878  reviewed  the 
subject  carefully,  pursuing  his  investigations  on  the  hyaline 
cartilage  of  the  triton,  tree-toad,  frog,  various  fishes,  the  guinea- 
pig,  total  pig,  and  the  human  embryo  in  health  and  disease. 
His  inquiries  were  especially  concerned  with  reference  to  the 
statement  of  Buetschli,  that  in  the  divisions  of  the  corpuscles, 
the  splitting  of  the  nucleus  and  cell-body  are  simultaneous. 
As  the  result  of  Dr.  Bigelow' s  work,  he  concludes  that  the  old 
theory  is  still  tenable,  viz.,  that  at  first  there  is  a  division  of 
the  nucleus,  and  that  subsequently  a  septum  is  found  in  the 
cell-body.  After  division  takes  place  the  matrix  of  the  carti- 
lage penetrates  between  the  corpuscles,  and  thus  two  cavities 
are  formed.  This  view  has  received  confirmation  from  very 
extended  and  elaborate  researches  by  Schleicher,  to  which 
Flemming  has  also  expressed  a  provisional  assent. 

Structure  of  the  cartilage-corpuscle. — According  to  Schlei- 
cher the  nuclei  are  provided  with  peculiar  filaments  and  gran- 
ules which  undergo  amoeboid  movements  when  they  are  in  the 
act  of  dividing.  In  the  cell-body  of  young  cartilage-corpuscles 
he  has  seen  no  network,  such  as  has  been  described  by  some 
later  writers  (Heitzmann,  Klein,  etc.),  though  in  the  adult  tissue 
peculiar  linear  markings  are  evident.  He  thinks  that  the  nu- 
cleus is  not  permeated  by  a  network,  but  is  homogeneous. 
Reticulated  appearances  are  apt,  he  thinks,  to  be  the  result  of 
using  reagents  that  alter  the  natural  quality  of  the  tissues. 
According  to  Flemming,  the  nucleus  of  the  cartilage-corpus- 
cles contains  a  network  which  gives  the  appearances  described 
as  "  coarsely  granular." 

In  the  drawings  of  this  author  the  cell-bodies  nowhere  exhibit  a  network, 
but,  on  the  contrary,  linear  markings,  which  have  often  a  concentric  direction. 
In  many,  the  internal  structure  is  represented  as  homogeneous.  The  conflict  of 
opinion  now  apparent  in  this  matter,  and  the  marked  differences  in  the  micro- 
scopic drawings  of  the  same  object,  make  it  apparent  that  these  topics  are  still 
to  be  regarded  as  subjudice. 

Structure  of  the  intercellular  substance. — According  to  Spina  there  is  an  intra- 
cellular  substance  in  cartilage  which  is  directly  continuous  with  the  intercel- 
lular substance,  which  itself  exhibits  an  extremely  delicate  network.  This 


88  MANUAL    OF   HISTOLOGY. 

condition,  which  he  regards  as  an  early  form  of  cartilage,  undergoes  changes, 
in  so  far  that  the  intercellular  network  is  enlarged  and  narrowed  so  as  to  give 
the  appearance  of  fascicles  or  bundles  of  parallel  fibres.  The  meshes  are  filled 
with  a  finely  granular  substance  which  is  thought  to  be  partly  formed  at  the 
expense  of  the  network.  The  method  employed  in  demonstrating  these  ap- 
pearances consisted  in  taking  the  articular  extremities  of  frog's  bones,  im- 
mersing them  three  to  four  days  in  alcohol,  then  cutting  thin  sections,  and 
finally,  examining  them  in  alcohol. 


BIBLIOGRAPHY. 

TILLMANNS.     Archiv  f.  mikrosk.  Anat.     X.     Bd.  X.  p.  401.     1874. 

BUDGE,  A.     Archiv  f.  mikrosk.  Anat;.     Bd.  XIV.,  S.  65.     1877. 

NYKAMP.     Archiv  f.  mikrosk.  Anat.     Bd.  XIV.,  S.  492.     1877. 

HEITZMANN.     Studien  am  Knochen  u.  Knorpel.     Wien.  med.  Jahrb.    1872.    V.  and 

H.'s  Bericht. 
BIGELOW,  W.  S.     Arch.  f.  mikrosk.  Anat.     XVI.,  2.     1878. 

SCHLEICHEB.      Ibid. 

FLEMMING.    Ibid. 

KLEIN  and  E.  NOBLE  SMITH'S  Atlas  of  Histology.     1879—1880. 

RANVIER.     Traite  technique  d'histologie.     1877. 

BUETSCHLI.     Zeitschr.  f.  wies.  Zool.     29,  p.  206. 

SPINA,  A.     Sitzb.  de  k.  Akad.  der  Wiss.     Bd.  LXXX.,  LXXXI.     1879,  1880. 


CHAPTEE  VII 

THE  CONNECTIVE  SUBSTANCE  GROUP.— Continued. 
BONE. 

THEEE  are  two  principal  varieties  of  bone  known  to  anato- 
mists, the  compact  and  the  cancellous  or  spongy.  The  former 
is  found  in  the  shafts  of  all  the  long  bones  of  the  body  and 
along  the  outer  surface  of  all  the  short  and  flat  bones.  The 
latter  occurs  in  the  articular  extremities  of  all  long  bones  and 
in  the  interior  of  all  short  and  flat  bones. 

Compact  tissue  consists  of  an  unyielding,  almost  inelastic, 
massive  framework,  which  is  traversed  by  networks  of  blood- 
vessels and  lymphatics,  and  perhaps  by  nerves.  The  dense 
organic  substance  forming  the  groundwork  of  all  bone — ossein 
— is  in  reality  nothing  but  a  form  of  connective  substance 
almost  precisely  resembling  ordinary  fibrous  tissue,  but  which 
is  evenly  infiltrated  with  minute  molecules  of  the  carbonates 
and  phosphates  of  lime  and  some  other  inorganic  salts.  These 
insoluble  matters  are  so  thoroughly  intermixed  with  the  fibrous 
tissue  that  they  give  it  great  solidity,  though  at  the  same  time 
they  restrict  its  flexibility,  and  therefore  increase  its  suscepti- 
bility to  fracture. 

Like  other  forms  of  the  connective-tissue  series,  it  contains 
corpuscles  that  are  disposed  in  a  regular  way  between  lamel- 
lae, which  here  correspond  to  the  fascicles  of  fibrous  tissue.  The 
province  of  these  corpuscles  is  doubtless  the  same  as  that  of 
other  connective-tissue  corpuscles,  viz.,  to  preside  over  the  nu- 
trition of  the  tissue  in  which  they  are  found. 

After  decalcification  by  strong  acids,  such  as  the  nitric  or 
muriatic,  if  the  residue  be  boiled  it  will  yield  gelatin  or  chon- 
drin. 

These  corpuscles  that  have  just  been  described  are  not  al- 


90  MANUAL    OF   HISTOLOGY. 

ways  easily  recognized,  and,  in  fact,  have  often  been  ignored 
by  writers  of  anatomical  text-books.  They  were  not  detected 
for  a  long  time,  because  the  capsules  in  which  they  are  em- 
bedded received  all  the  attention,  and  were  even  called  'bone- 
corpuscles.  But  when  it  was  discovered  by  Yirchovv  that 
these  bodies  had  nuclei,  and  that  they  could  be  separated,  to- 
gether with  their  processes,  from  the  bone,  it  was  supposed 
that  the  nutrition  of  the  tissue  was  maintained  through  them, 
acting  in  the  capacity  of  hollow  tubes.  This  view  Virchow  at 
one  time  supported.  Subsequently  it  was  discovered  that  in- 
jection fluids  could  be  forced  into  the  canaliculi  and  round 
about  the  corpuscles,  so  that  three  facts  became  assured  :  (1) 
the  existence  of  capsules  in  the  bony  substance  with  radiating 
and  anastomosing  passages,  the  lacunae  and  canaliculi  ;  (2)  the 
presence  of  nucleated  and  branched  corpuscles  in  the  lacunae ; 
and  of  spaces  (3)  about  the  nucleated  corpuscles  and  their 
processes,  suitable  for  the  movement  of  fluids  designed  for  the 
nutrition  of  the  part. 

The  structure  of  bone  then  became  clear,  and  its  similarity 
with  other  connective  substances  well  established.  These  bony 
canaliculi  extend  to  the  wall  of  the  Haversian  canal,  the  great 
channel  conveying  the  blood-vessels  and  larger  lymphatics. 
Thus  a  lymph-canalicular  system  permeates  the  bone  in  close 
connection  with  the  blood-vessels,  bathing  every  bone-cor- 
puscle. 

When  a  cross-section  is  made  of  any  long  bone,  it  will  be 
observed  that  most  of  the  lamellae  have  a  concentric  arrange- 
ment about  each  Haversian  canal  (Fig.  35,  b).  But  it  will  also 
be  seen  that  there  are  other  groups  of  lamellae  whose  arrange- 
ment is  slightly  different.  For  example,  at  the  periphery  of 
the  bone  their  direction  is  parallel  with  the  surface. 

Such  lamellae  may  be  represented  at  a.  They  are  known  as 
the  intermediate  or  circumferential  (Tomes  and  De  Morgan). 
Another  group,  only  partly  encircling  each  canal,  is  known  as 
the  peripJieric  or  interstitial,  c.  The  first  mentioned,  imme- 
diately about  the  canal,  are  the  concentric,  b. 

Schaefer  believes  with  Sharpey  that  each  lamella  consists  of  fibres  crossing 
each  other  diagonally,  and  separated  on  either  side  by  a  homogeneons  layer. 
According  to  Von  Ebner,  the  peculiar  cross  striations  belong  only  to  Canada 
balsam  preparations  that  are  old.  These  markings  are  due  to  the  peculiar 
refractive  power  of  the  balsam  which  fills  the  canaliculi. 


THE    CONNECTIVE    SUBSTANCE    GKOUP. 


91 


The  arrangement  just  described  is  found  in  all  compact 
bone  where  there  is  any  considerable  thickness,  but  when,  as 
in  flat  bones,  the  cortex  is  very  thin,  the  lamellae  often  pursue 
a  straight  arid  parallel  course.  Some  of  these  lamellae  or  plates 
exhibit  transverse  striations  ;  others  are  homogeneous. 

In  Fig.  35  may  be  seen  the  lacunae  lying  between  the 
lamellae.  They  appear 
as  dark  spaces  disposed 
at  quite  regular  intervals 
and,  having  their  long 
axes  parallel  with  the 
course  of  the  lamellae. 
Laterally  each  corpuscle 
gives  off  numbers  of  pro- 
cesses, many  of  which 
branch,  while  all,  or  near- 
ly all,  anastomose  with 
corresponding  branch- 
lets  of  other  corpuscles- 
A  branchlet  is  also  given 
off  from  the  end  of  each 
corpuscle,  and  forms  a 
connection  with  the  adjacent  bodies  lying  in  the  same  inter- 
lamellar  space  and  in  the  same  plane. 

The  Haversian  canals  form  a  broad-meshed  network  through- 
out the  bone,  establishing  a  communication  between  the  central 
marrow  cavity  and  the  external  surface  of  the  bone  (Fig.  36). 

The  arrangement  of  parts  comprised  by  each  Haversian 
canal,  with  its  investing  lamellae,  and  interposed  lacunae  and 
their  anastomosing  carialiculi  constitutes  an  Haver sian  system. 
Though  found  mainly  in  the  compact  tissue,  they  may  also  be 
seen  in  the  large  trabeculae  of  the  spongy  substance.  As  seen 
in  Fig.  36,  the  Haversian  canals  form  a  network  of  which  the 
longitudinal  tubes  are  the  larger  and  longer.  Besides  convey- 
ing blood-vessels  and  lymphatics  they  have  a  certain  amount 
of  connective  tissue  which  varies  according  to  the  locality,  and 
establishes  a  more  or  less  complete  connection  between  the  con- 
nective tissue  of  the  marrow  cavity  and  of  the  periosteum. 

In  young  bone  this  is  well  seen ;  in  adult  bone  the  direct 
continuity  can  with  difficulty  be  traced,  as  the  vessels  are  apt 
to  till  the  tubes  pretty  completely. 


PIG.  35. — Transverse  section  of  human  femur,  deprived  of 
inorganic  material  by  hydrochloric  acid.    (Rollett.) 


92 


MANUAL    OF   HISTOLOGY. 


Preparation  of  dry  bone. — In  order  to  study  the  char- 
acteristics which  have  just  been  described,  any  human  long 
bone  may  be  taken.  It  should  be  stripped  of  its  soft  parts, 
bleached,  and  well  dried.  Thin  sections  are  then  to  be  made 
both  in  a  longitudinal  and  transverse  direction,  with  a  watch- 
spring  saw. 

Next,  cleanse  them  well  in  water  to  which  a  little  bicar- 
bonate of  soda  has  been  added ;  then  place  on  a  whetstone 
and  grind  down  by  rubbing  backward  and  forward  with  the 

finger  until  they  are  suffi- 
ciently thin  ;  or  the  sections 
may  be  placed  between  two 
plates  of  ground  glass  and 
rubbed  down. 

Finally,  when  so  thin  that 
type  may  be  read  through 
them,  mount  either  dry  or 
in  Canada  balsam  or  dam- 
mar varnish.  All  the  char- 
acteristics already  described 
may  then  be  seen. 

Preparation  of  decalci- 
fied bone. — Another  method 
consists  in  first  removing  the 
earthy  salts.  If  it  is  desira- 
ble to  accomplish  the  work 
rapidly,  cut  the  bone  to  be 
prepared  into  the  smallest 
available  pieces  and  immerse 
from  four  to  five  days  in  a  10 
per  cent,  watery  solution  of 

Fio.  36. -Longitudinal  section  of  human  nlna,  show-    hydrochloric  acid, 
ing  the  Ha versian  canals  forming  meshes.    (Rollett.)  m,  ,     ,.  »      ,,  . 

The  completion  of    this 

process  may  be  determined  by  testing  the  bone  with  a  fine  cam- 
bric needle.  So  long  as  it  meets  with  resistance,  the  presence 
of  the  bone-earths  is  certain ;  on  the  other  hand,  if  it  enter 
easily,  the  process  of  decalcification  is  over,  and  the  piece  ready 
for  cutting. 

Now  wash  thoroughly  in  water,  so  as  to  remove  the  acid, 
place  in  80  per  cent,  alcohol,  gradually  increasing  the  strength 
to  95  per  cent.  The  specimen  is  then  ready  for  use  and  may 


THE   CONNECTIVE   SUBSTANCE    GROUP.  93 

be  treated  precisely  as  any  other  tissue  of  the  body.  If  more 
time  is  at  the  disposal  of  the  student,  chromic  acid  may  be 
used  in  a  J  per  cent,  solution.  This  process  is  rather  slow,  re- 
quiring several  months.  It  may  be  materially  hastened  by  the 
use  of  nitric  acid  (2  per  cent.).  It  has  been  found  that  after 
immersion  in  chromic  acid  for  a  few  days,  the  soft  parts  are 
rendered  insensible  to  the  action  of  other  strong  acids,  such  as 
nitric  and  hydrochloric,  when  used  in  the  dilute  form.  These 
chromic  acid  preparations  are  exceedingly  beautiful  objects 


FIG.  37.  —Bone  lacunaa  with  their  processes.    (Rollett. ) 

when  seen  with  low  powers.  The  matrix  is  of  a  deep  grass 
green.  If  a  thin  section  is  stained  with  borax-carmine  (Arnold's 
formula)  the  bone-corpuscles  and  connective  tissue  are  stained 
red,  and  the  contrast  of  color  brings  out  the  finer  elements 
very  distinctly. 

Picro-carmine  may  also  be  used,  and  then  the  muscular  tis- 
sue, if  any  chance  to  adhere  to  the  bone,  is  stained  yellow  ;  or 
eosine  and  hsematoxylin  may  be  used  instead  of  borax  car- 
mine, and  thus  very  excellent  examples  of  triple  staining  pro- 
cured. Sometimes  a  saturated  solution  of  picric  acid  is  em- 
ployed to  decalcify,  but  the  excess  of  acid,  after  taking  out 
the  bone-earths  should  be  thoroughly  removed  by  soaking  in 


94  MANUAL    OF    HISTOLOGY. 

water  before  immersion  in  any  staining  fluid.  In  preparing  a 
specimen  for  cutting  with  the  knife  it  may  conveniently  be 
held  in  the  hand,  or,  if  the  microtome  is  used,  the  bone  may 
be  embedded  in  the  ordinary  mixture  of  wax  and  oil,  pith,  or 
liver,  according  to  methods  already  described.  Rutherford  re- 
commends glycerine  jelly  for  this  purpose. 

Any  of  these  plans  of  preparing  decalcified  bone  will  reveal 
the  presence  of  the  bone-corpuscles  within  the  lacunae.  These 
will  be  found  to  correspond  quite  closely  in  size  and  shape 
with  the  cavities.  They  may  also  be  shown  to  have  a  direct 
continuity  with  the  connective- tissue  corpuscles  of  the  perios- 
teum. In  growing  bone  this  is  more  evident.  A  nucleus  can 
also  sometimes  be  seen  in  the  bone-corpuscle.  In  Fig.  36 
the  lacunae,  with  their  canaliculi,  are  well  shown. 

Sharpens  perforating  fibres. — Attached  to  the  outer  sur- 
face of  compact  tissue,  and  penetrating  the  bone  at  right  an- 
gles, are  certain  fibres  which  have  been  named  after  Sharpey, 
their  discoverer. 

Take  a  flat  bone  of  the  skull  that  has  been  decalcified,  seize 
pieces  with  the  forceps,  tear  them  out  from  the  surface,  and 
examine  in  water.  In  some  of  the  fragments  the  bundles  of 
fibres  will  be  seen  ;  in  others  the  lamellae,  perforated  for  the 
fibres.  If  a  portion  of  tendon  adhere  to  the  bone,  and  a  sec- 
tion be  made  through  the  two  at  their  line  of  apparent  junc- 
tion, it  will  be  seen  that  the  tendon-fibres  are  continuous  in 
the  bone  with  Sharpey' s  fibres. 

A  very  prevalent  view  is  that  they  constitute  the  remains  of 
the  periosteal  processes,  which  we  shall  see  are  largely  con- 
cerned with  the  ultimate  development  of  bone. 

Cancellous  tissue. — All  of  the  elements  of  bone,  that  go  to 
make  up  a  Haversian  system,  are  found  in  the  cancellous 
tissue,  so  that,  in  this  respect,  it  does  not  differ  from  the  com- 
pact. The  chief  peculiarity  lies  in  the  marrow  cavities,  or 
channels,  as  they  might  appropriately  be  called,  and  they  indi- 
cate either,  on  the  one  hand,  that  the  bone  is  passing  through 
a  developmental  stage  ;  or  that  it  is  being  rarefied  by  a  process 
of  retrograde  metamorphosis  ;  or,  finally,  that  it  has  reached  a 
stadium  of  repose  in  either  of  the  first-named  changes.  These 
points  will  be  further  particularized  when  the  growth  and  de- 
velopment of  bone  is  explained,  but  the  reader  is  now  prepared 


THE    CONNECTIVE    SUBSTANCE    GEOUP.  95 

for  the  rather  remarkable  proposition  that  compact  bone  is 
formed  out  of  spongy,  and  spongy  out  of  compact. 

These  marrow  channels  are  a  series  of  branching  and  anasto- 
mosing tubes,  rich  in  corpuscular  elements  and  vessels.  In 
young  bone  the  latter  are  known  as  red  marrow.  When  a 
longitudinal  section  has  been  made  through  a  tubular  bone,  it 
will  be  seen  that  the  channels  are  enclosed  in  an  osseous  net- 
work, whose  meshes  differ  much  in  shape.  In  the  articular 
extremities  they  are  long  and  narrow ;  at  other  points,  more 
nearly  quadrilateral. 

There  is  a  second  variety  of  marrow,  known  as  yellow,  which 
is  found  in  the  central  cavity  of  the  long  bones.  The  yellow 
color  is  due  to  the  presence  of  fat,  though  it  also  contains 
peculiar,  small,  colorless  corpuscles,  not  unlike  the  leucocytes 
of  the  blood,  and  known  as  marrow-cells,  together  with  the 
ordinary  branched  and  nucleated  connective-tissue  corpuscles, 
also  large  multi-nucleated  bodies  that  are  usually  granular  and 
sometimes  striated,  and  blood-vessels.  The  large  corpuscles 
are  the  myeloplaxes  of  Robin  (giant-cells). 

The  red  marrow  also  contains  marrow-cells,  though  but  few 
fat-cells.  It  is  remarkable  for  being  the  seat  of  the  peculiar 
nucleated  blood-corpuscles  that  have  been  described  by  Neu- 
mann and  Bizzozero.  They  are  transitional  between  the  white 
and  the  red  in  size,  and  have  a  uniform  yellowish  green  color 
(Klein). 

The  authors  above  referred  to  found  the  nucleated  corpuscles  in  the  red 
marrow  of  the  ribs  and  bodies  of  the  vertebra ;  they  resembled  blood-corpus- 
cles that  are  found  in  the  human  embryo,  and  were  regarded  as  evidence  that 
the  bones  have  bloodmaking  properties.  Later  researches  (Orth  and  Litten) 
have  seemed  to  corroborate  these  views,  and  to  have  shown  that  in  certain 
morbid  states  of  the  blood,  as  in  carcinoma,  phthisis,  and  syphilis,  an  effort  of 
this  kind  is  made  for  the  relief  of  the  constitutional  infection.  Experiments 
upon  dogs  have  also  added  further  testimony  and  have  shown  that  after  extreme 
artificial  anaemia  there  is  a  new  formation  of  blood-globules,  in  which  the 
nucleated  bodies  play  an  active  part,  together  with  other  elements,  such  as  the 
giant-corpuscles  of  Hayem,  etc.  These  views,  however,  have  met  with  opposi- 
tion, and  Eutherford  ("  Pract.  Histology,"  p.  88)  maintains  that  the  nucleated 
corpuscle  is  an  indication  of  corpuscular  disintegration  rather  than  of  new- 
formation. 

The  periosteum  is  a  layer  of  dense  fibrous  tissue  closely 
covering  the  bone,  and  connected  with  it  by  a  thinner  layer  of 


96  MANUAL    OF   HISTOLOGY. 

looser  texture.  The  external  portion  may  be  composed  of  sin- 
gle, double,  or  treble  laminae  of  varying  thickness.  The  inner 
or  osteogenetic  portion  is  of  great  interest  and  importance, 
as  it  contains  the  osteoblasts,  which  are  active  agents  in  the 
formation  of  a  great  part  of  all  bones,  as  we  shall  presently 
see. 

Development  of  bone. — Views  as  to  the  method  by  which  bone 
is  formed  have  undergone  great  changes  within  the  past  few 
years,  and  it  may  be  stated  that  most  modern  observers  have 
given  in  their  adhesion  to  the  theory  that  bone  is  not  developed 
by  a  calcification  of  cartilage,  but  by  a  long  and  complicated 
series  of  changes  inaugurated  by  the  corpuscles  of  the  marrow 
cavities,  on  the  one  hand,  and  those  of  the  periosteum,  on  the 
other.  These  conclusions  have  been  the  result  of  very  extended 
researches  conducted  by  a  variety  of  methods  and  upon  many 
kinds  of  animals. 

As  the  mode  of  growth  in  man  and  horned  cattle  is  identical, 
a  good  method  of  procedure  is  as  follows.  Take  the  hoof  of  a 
yearling  bullock,  and,  removing  the  bones,  macerate  them  a 
few  days  in  a  10  per  cent,  watery  solution  of  h37drochloric  acid 
and  then  in  chromic  acid  (gr.  ij. —  lj.).  In  a  few  days  they 
will  be  decalcified  sufficiently  to  allow  of  a  thin  section  being 
shaved  off  from  the  surface  so  as  to  include  parts  where  ossifi- 
cation has  already  commenced.  The  sections  may  then  be 
stained  in  a  neutral  solution  of  carmine  and  mounted.  The 
gradual  stages  between  the  advancing  bone  and  the  liquefying 
cartilage  can  now  be  studied.  Following  the  changes  from  the 
surface  of  the  articulation  toward  the  centre  of  the  bone,  there 
is  seen  at  first,  beneath  the  fibrous  layer,  a  stratum  of  hyaline 
cartilage.  The  corpuscles  are  long,  flattened,  and  lie  parallel 
with  the  surface.  Passing  to  a  greater  depth  they  become 
larger,  and  increase  in  number  by  gradual  progression.  As 
these  capsules  enlarge  and  their  contents  multiply,  they 
begin  to  be  arranged  about  the  wall  of  the  cavity,  while 
the  matrix  gradually  wastes  away.  A  little  farther  and 
there  is  a  deposit  of  calcific  material  in  the  intercapsular  sub- 
stance. Another  step  internally  and  the  cartilage  capsules 
have  in  part  coalesced,  and  now  they  are  beginning  to  be  filled 
by  the  marrow  tissue  pushing  up  from  the  central  parts  of  the 
bone.  When  the  connective  tissues  and  vessels  that  constitute 
this  arborescent  growth  have  entered  the  capsules,  the  corpus- 


THE    CONNECTIVE    SUBSTANCE    GROUP.  97 

cles  that  line  them  are  called  osteoblasts.  Whether  or  not  they 
are  identical  with  the  cartilage-corpuscles,  or  belong  to  the 
budding  marrow-processes,  seems  to  be  a  matter  of  doubt. 
Klein  intimates  that  the  cartilage-corpuscles  disintegrate.  Ran- 
vier  has  seen  no  proof  of  it.  It  is  probable  that  some  of  the 
cartilage-corpuscles  persist,  certainly  to  a  limited  extent, 
and  preside  over  the  remains  of  the  calcified  cartilage.  The 
bulk  of  the  new  bone  is  made  up,  however,  of  new  material 
which  is  deposited  under  the  form  of  concentric  lamellae  about 
the  marrow  cavities,  most  likely  by  a  proliferation  of  the 
osteoblasts. 

These  changes  may  all  be  observed  to  advantage  in  the 
specimen  just  mentioned,  and  the  successive  gradations  of  the 
process  can  be  conveniently  magnified,  so  as  to  be  easily  seen, 
by  making  sections  obliquely  to  the  surface  of  the  bone.  With 
a  low  power  the  specimens  will  have  uncommon  beauty,  as  the 
corpuscles  take  the  carmine  well,  while  the  interstitial  tissue  is 
of  a  bright,  transparent  grass-green. 

In  a  vertical  section  of  a  long  bone,  while  the  process  is 
essentially  the  same,  there  are  some  modifications  in  the  suc- 
cessive steps.  Thus  the  spongy  bone  of  the  epiphysis  en- 
croaches on  the  cartilage,  causing  it  to  be  absorbed  in  the  man- 
ner already  described,  but  the  intermediary  cartilage,  lying 
between  the  epiphysis  and  diaphysis,  is  seen  to  have  its  cor- 
puscles arranged  in  long  lines  parallel  with  the  axis  of  the 
bone  ("step-ladders").  The  bone  meshes  of  the  encroaching 
bone  are  also  shaped  in  correspondence  with  the  cartilage  cap- 
sules, that  is,  they  are  long  and  narrow. 

Formation  of  bone  through  the  medium  of  cartilage. — The 
successive  changes  in  this  species  of  bone  development  have 
been  best  described  by  Klein.  According  to  him  the  hyaline 
cartilage  that  is  destined  to  prepare  the  way  for  bone  is  covered 
with  perichondrium,  consisting  like  the  periosteum  of  two 
layers.  This  membrane  does  not  at  first  contain  mature  fibrous 
tissue,  but  merely  the  rudiments  of  it,  under  the  form  of  spin- 
dle-shaped corpuscles  ;  its  internal  layer,  however,  is  early  pro- 
vided with  spherical  corpuscles,  the  future  osteoblasts,  and  is 
rich  in  vessels. 

Subsequently  this  osteogenetic  envelope  puts  out  processes 
(periosteal  processes,  Virchow)  that  penetrate  into  the  carti- 
lage-capsules, which,  melting  as  the  external  growth  makes  its 
7 


98  MANUAL    OF   HISTOLOGY. 

way  inward,  develop  communications  between  the  capsules,  so 
that  in  this  way  a  cartilaginous  network  is  formed  that  is  filled 
with  the  arborescent  tissue.  This  change  in  the  cartilage, 
which  is  characterized  by  absorption  and  rarefaction,  is  called 
chondro-porosis. 

At  a  more  advanced  stage  the  cartilage  around  the  oldest 
channels  has  become  transparent  in  places,  while  the  walls  are 
irregular,  because  portions  of  calcified  trabeculse  project  into 
them.  These  irregular  spaces  are  called  primary  marrow 
cavities.  Now  upon  the  walls  may  be  seen,  not  the  cartilage- 
corpuscles,  but  the  osteoblasts,  which  are  proceeding  to  develop 
concentric  layers  of  osseous  tissue. 

When  this  process  has  been  completed,  the  osseous  tissue 
will  be  found  to  have  replaced  the  calcified. cartilage,  and  true 
bone  has  been  formed.  But  this  action  may  be  no  sooner 
completed  than  absorption  will  again  commence,  and  at  first  in 
the  last  or  most  internal  layer  of  the  Haversian  system.  This 
process  is  essential  for  the  development  of  the  central  marrow 
cavity.  After  an  Haversian  system  has  been  removed,  the 
matrix  will  also  disappear. 

Now,  while  this  cavity  is  filling  up  with  marrow  a  gradual 
development  of  bone  is  taking  place  from  the  periosteum, 
which  slowly  encroaches  upon  the  bone  whose  formation  we 
have  just  described. 

This  last  stage  results  in  the  formation  of  adult  bone. 
When  it  has  been  completed  all  the  first  formed  bone  has 
been  absorbed  before  it.  This  periostea!  or  metaplastic  bone 
is  at  first  spongy,  as  is  all  new  bone ;  in  the  fulfilment  of  its 
task  it  next  appears  to  form  compact  bone,  and  then  part  of 
this  latter  is  rarefied,  as,  for  example,  along  the  wall  of  the 
central  cavity.  Thus,  as  we  have  already  seen,  compact  bone 
is  formed  from  spongy,  and  spongy  from  compact.  The  peri- 
pheric  or  interstitial  lamellae  are  either  the  remains  of  calcified 
and  unabsorbed  trabeculse,  or  perhaps  the  walls  of  other  Haver- 
sian systems  forming  sides  of  the  bony  network. 

Formation  of  bone  from  membrane. — This  second  method 
of  bone-formation  is  seen  in  the  bones  of  the  skull  and  face. 
The  steps  are  precisely  similar  to  those  already  described.  The 
inner  layer  of  the  periosteum,  which  is  lined  with  osteoblasts, 
produces  both  matrix  and  bone  corpuscles  by  a  process  of  bud- 
ding. The  change  first  begins  at  the  points  of  ossification. 


THE    CONNECTIVE    SUBSTANCE    GKOUP.  99 

At  first  the  bone  is  spongy,  but  later  absorption  takes  place — 
osteoporosis.  Around  some  of  the  marrow- tubes  concentric 
lamellae  are  formed,  and  in  this  way  a  Haversian  system  de- 
velops. The  unabsorbed  portions  of  the  trabeculae  are  thought 
to  constitute  the  lamellae  known  as  the  intermediary.  Com- 
pact tissue  is  thus  formed  from  spongy.  This  theory,  which 
has  been  placed  in  its  present  acceptable  light  by  Klein,  is  very 
simple  and  appears  to  accord  with  observation,  and  explains 
all  the  phenomena.  Yet  those' who  have  believed  in  the  direct 
transmutation  of  cartilage  into  bone  are  still  in  the  field. 
Kolliker  maintains  that  both  views  are  correct. 

According  to  this  last  named  author  the  differences  between  primary  or 
primordial  and  the  tegumentary  or  secondary  bones  are,  from  a  morphological 
point  of  view,  sharp  and  complete.  The  former  are  ossifications  of  the  carti- 
laginous skeleton. 

The  tegumentary  are  never  cartilaginous  at  first ;  the  primordial  bones,  on 
the  other  hand  are,  without  exception,  formed  from  cartilage.  The  method  and 
manner  in  which  bony  tissue  is  formed  is  the  same  in  both  bones.  The  pri- 
mordial skeleton  in  the  lower  vertebrates  ossifies  only  in  part  from  the  peri- 
chondrium,  in  part  perichondrally,  and,  in  part,  endochondrally. 

According  to  Kassowitz,  in  the  tuberosities  and  spines  of  the  bones  the 
periosteal  processes  of  the  periosteum,  which  develop  the  bone,  are  primarily 
cartilaginous,  the  fibrillated  tissue  being  converted  into  hyaline  cartilage, 
which  is  at  first  calcified  and  then  undergoes  direct  conversion  into  bone. 

According  to  the  experiments  of  Strawinsky  a  transplanted  periosteum  will 
develop  either  bone  or  cartilage,  when  the  conditions  are  favorable.  The  con- 
ditions of  nutrition  determine  which  it  shall  be.  When  the  supply  is  best, 
cartilage  is  formed  ;  when  poorest,  bone. 

The  earliest  evidences  of  ossification  were  seen  by  this  observer  between 
the  fourth  and  fifth  days.  The  formation  of  vessels  preceded  that  of  bone. 
Absorption  commenced  between  the  second  week  and  the  second  month.  The 
new  formation  of  periosteum  is  partly  derived  from  the  border  of  the  wound 
and  partly  from  the  Haversian  canals,  which  contain  a  small  amount  of  connec- 
tive tissue. 

Development  of  bone  and  absorption. — It  has  been  seen 
that  these  two  processes  go  on  hand  in  hand.  As  soon  as  the 
periosteum  has  commenced  to  deposit  new  layers  of  bone  on 
the  surface  of  the  primary  spongy  bone,  absorption  takes  place 
along  the  marrow  canal.  First  of  all,  as  we  have  already  said, 
the  innermost  of  the  concentric  lamellae  yield.  In  this  way 
the  Haversian  canals  are  widened  and  become  Haversian  spaces, 
as  they  were  at  first ;  then  the  interstitial  lamellae,  and  finally 


100  MANUAL    OF   HISTOLOGY. 

the  spaces  disappear,  and  in  place  of  them  there  is  a  single 
dilated  central  cavity. 

Howship's  lacunce  are  the  pits  or  lacunae  seen  in  bone 
beneath  the  periosteum.  They  usually  contain  a  multinuclear 
corpuscle  (giant-cell),  which  is  in  some  way  related  to  absorp- 
tion, and,  therefore,  has  received  the  name  osteoclast  (Kolli- 
ker).  It  has  been  surmised  (Klein)  that  they  are  the  agents  by 
which  an  acid  is  formed  that  dissolves  the  lime-salts.  Whether 
they  are  developed  out  of  the  osteoblasts  or  not  is  a  matter  of 
uncertainty. 

All  the  steps,  both  in  development  and  absorption  of  bone, 
have  been  carefully  studied  and  placed  upon  a  most  satisfac- 
tory foundation  (Lieberkuhn  and  Bermann).  The  absorption 
of  bone  has  also  been  actually  proved  by  measurements  of  the 
bones  in  children  (Schwalbe).  By  comparing  the  bones  of  the 
third  and  fourth  years  of  life,  it  was  found  that  the  marrow 
cavity  had  enlarged  in  the  latter,  while  the  compact  bone  had 
diminished  in  thickness.  The  change  commenced  at  the  sixth 
month.  This  physiological  process  is  closely  allied  to  the 
pathological  one  exhibited  in  rachitis ;  in  the  latter  the  de- 
velopment of  bone  from  the  periosteum  has  the  character  of 
foetal  bone,  but  the  formation  of  the  lamellsD  is  slow  and 
incomplete. 

It  has  been  claimed  that  the  growth  of  bone  takes  place 
by  an  expansion  of  the  intercellular  substance  (Strelzoff),  but 
this  is  denied  (Kolliker,  Wegener,  Schwalbe,  and  others). 
The  ossein  appears  to  increase  somewhat,  but  it  is  at  the  ex- 
pense of  the  bone- corpuscles,  which  are  thereby  diminished  in 
size. 

Formation  of  callus. — The  method  is  the  same  as  in  the  de- 
velopment from  periosteum.  A  corpuscular  blastema  is  devel- 
oped from  the  periosteum  and  intermuscular  tissue.  This 
presses  in  between  the  fibres  and  bundles  of  the  loose  con- 
nective tissue,  pressing  them  asunder,  assuming  considerable 
volume.  This  new  tissue  is  hyaline  cartilage.  In  from  three 
to  six  weeks  it  ossifies,  being  in  part  directly  transformed  into 
bone,  in  part  mediately,  i.e.,  through  the  agency  of  medullary 
spaces  and  osteoblasts.  Where  the  extremities  of  the  bone  are 
widely  separated  there  is  a  formation  of  bone  in  the  medullary 
spaces  of  the  broken  ends  of  the  bones.  The  pre-existing  bone- 
corpuscles  have  no  part  in  the  new-formation.  This  compact 


THE   CONNECTIVE   SUBSTANCE   GROUP.  101 

bone  thus  formed  will  be  absorbed  in  a  few  months,  in  its 
internal  portions,  by  rarefying  ostitis,  so  that  the  marrow  cavi- 
ties of  the  broken  diaphysis  will  be  in  communication. 


BIBLIOGRAPHY. 

The  student  is  referred,  for  further  particulars,  to  Klein's  Atlas  of  Histology,  Ban- 
vier's  Traite  technique  d'histologie,  Strieker's  Manual  of  Histology,  and  also  to  the 
following  recent  writers : 

SCHAEFER.     Pract.  Histology.     1872. 

LIEBERKUHN  and  BERMANN.     Ueber  Kesorption  der  Knochensubstanz.     1877. 

AUFRECHT.     Ueber  Riesenzellen  in  Elfenbeinstiften.     Med.  Centralblatt,  No.  26. 

Jahresb.  d.  Fortschritte  der  Anat.  und  Phys.     1878. 
ARNOLD,  J.    Virchow's  Archiv.     Bd.  71,  p.  17.    1877. 
VON  EBNER.     Sitzungsbericht  der  Wiener  Akad.     III.  Abtheil.    Bd.  75.    Hofmann 

und  Schwalbe's  Jahresb.     1878. 

KASSOWITZ.     Med.  Centralblatt,  No.  5.     Hofmann  und  Schwalbe's  Jahresb.     1878. 
SCHWALBE.    Sitzungsb.  dermed.  naturwiss.  Gesellschaf t  zu  Jena.    1877.  H.  und  S.'s 

Jahresb.    1878. 

STRAWINSKY.    Ueber  Knochenresorption.     H.  und  S.'s  Jahresbericht,  p.  109,  1878. 
LITTEN,  M.,  and  ORTH,  J.     Berliner  klin.  Woch.    No.  51,  p.  743.    1877. 
KOLLIKEB.    Entwickelungsgeschichte.    V.  und  S.'s  Jahresb.    1878. 


CHAPTER  VIII. 

THE  TEETH. 

FROM  the  standpoint  of  descriptive  anatomy,  every  tootli  is 
composed  of  three  parts  :  (1)  the  crown,  that  portion  which 
stands  above  the  level  of  the  mucous  membrane  of  the  gum  ; 
(2)  the  neck,  a  constricted  part  at  the  level  of  the  gum  ;  and  (3) 
the  root,  which  terminates  in  one  or  more  fangs,  and  is  firmly 
embedded  in  the  alveolar  process  of  the  jaw.  Each  fang  also 
is  pierced  from  below  by  a  canal,  which  extends  up  into  the 
crown,  and  is  filled  by  a  soft  material  rich  in  nerves  and  ves- 
sels, called  the  pulp,  which  has  the  special  province  of  sup- 
plying nutriment  to  the  dense  tissue  about  it. 

From  a  histological  point  of  view,  every  tooth  may  be  di- 
vided into :  1,  enamel ;  2,  dentine,  or  ivory  ;  3,  cement,  or  true 
bone.  The  enamel  forms  the  covering  for  the  crown,  the  cement 
for  the  root ;  but  they  meet  at  the  neck,  and  there  the  cement 
slightly  overlaps.  The  ivory  or  dentine  lies  intermediate  be- 
tween the  outer  coatings  and  the  pulp. 

The  enamel. — This  substance,  which  is  the  hardest  met  with 
in  the  body,  consists  of  a  series  of  long  polyhedral  columns 
grouped  in  bundles  and  disposed  mostly  at  right  angles  to  the 
surface  of  the  dentine  which  lies  beneath  it.  Each  column  or 
pillar  is  a  hexagonal  prism,  having  a  diameter  varying  between 
nrJiro  and  -^5^  inch.  When  viewed  in  cross-section  these  col- 
umns look  like  a  tesselated  pavement.  They  are  not,  however, 
closely  applied  to  one  another,  but  have  interspaces  which  are 
said  to  be  filled  with  a  homogeneous  substance  or  fluid. 

All  of  the  groups  of  columns  do  not  stand  vertical  to  the 
dentine  ;  some  are  parallel  to  it,  and  thus  are  interwoven  with 
the  vertical  ones.  This  crossing  of  the  fibres  produces  an 
alternation  of  light  and  dark  bands  (Fig.  38,  1).  But  there  are 
other  systems  of  markings.  In  the  same  figure  are  wavy 


THE   TEETH. 


103 


lines  running  parallel  to  the  surface.  These  are  the  "  brown, 
parallel  stripes  of  Retzius"  They  pursue  a  somewhat  curved 
course.  No  unity  of  opinion  exists  about  their  significance, 
one  (Hertz)  attributing  them  to  deposits  of  pigment,  another 
(Von  Bibra)  to  the  pres- 
ence of  the  oxide  of  iron. 
Still  other  striae  are  ob- 
served, and  are  thought 
to  represent  the  zigzag 
or  spiral  course  of  the 
enamel  prisms.  It  is 
observed  that  when  the 
prisms  are  isolated,  which 
can  be  accomplished  by 
immersion  in  a  dilute  hy- 
drochloric acid  solution, 
they  have  a  somewhat 
spiral  form,  and  have 
bulging  sides  and  cross 
markings,  the  signifi- 
cance of  which  will  be 
alluded  to  at  another 
place. 

Near  the  line  of  the 
dentine  there  are  spaces 
between  the  prisms  which 
are  continuous  with  the 
cavities  in  the  dentine. 
These  are  called  the  in- 
terglobular  spaces  of 
Czermak.  They  also  oc- 
cur at  irregular  intervals 
in  the  dentine. 

%         Tn         Trrmno*       cnVn£»r»tc      section,  magnified  15  diameters.     1,  enamel  with  decussating 
111        7°  IDjeC      .      and  parallel  string  ;   2,  dentine  with  Schreger's  lines ;   3,  eel 

there  is  a  delicate  mem- 
brane covering  the  sur- 
face of  the  enamel.  It  is  composed  of  laminated  epithelial 
scales,  and  corresponds  to  the  corneous  layer  of  the  skin,  of 
which,  indeed,  it  represents  the  vestiges. 

The  dentine  or  ivory  (Fig.  38,  2)  consists  of  a  dense  and 
hard  matrix  impregnated  with  the  salts  of  lime.     It  contains 


FIG.  38.— Premolar  tooth  of    the  cat,  in  situ.      Vertical 


and  parallel  striae  ;  2,  dentine  with  Schreger's  lines ;  3,  ce- 
ment ;  4,  periosteum  of  the  alveolus ;  5,  inferior  maxillary 
bone.  (Waldeyer.) 


104 


MANUAL    OF   HISTOLOGY. 


numerous  passages  having,  like  the  enamel  prisms,  a  direction 
at  right  angles  to  the  surface  of  the  bone.  These  passages,  the 
dentinal  canals,  are  united  with  one  another  laterally  by 
minute  oblique  branches,  and  form  undoubtedly  open  channels 
of  communication  between  the  pulp  cavity  and  the  spaces  be- 
tween the  enamel  prisms  in  the  crown  and  the  bone  lacunae  of 

the  cement  in  the  fang.    Each  canal 
— -^=^^^E^^^       is  lined  with  a  particularly  delicate 
and  resistant  membrane,  the  den- 
tinal sheath  of  Neumann. 

Upon  the  internal  surface  of  the 
dentine,  or  the  external  surface  of 
the  pulp- tissue,  is  the  layer  of 
odontoblasts  (Schwann).  These  cor- 
puscles, according  to  Waldeyer, 
have  long  branching  processes  ex- 
tending in  three  directions,  inward 
into  the  pulp-cavity,  outward 
through  the  dentinal  channels, 
forming  the  dentinal  fibres  of 
Tomes,  and  laterally  so  as  to  form 
connection  with  adjacent  corpus- 
cles. On  the  outer  surface  of  the 
dentine  the  canals  connect  with 
the  interglobular  spaces  of  Czer- 
mak,  and  they  in  turn  are  con- 
tinuous with  interstices  between 
the  enamel  prisms.  The  dentinal 
tubules  never  appear  to  be  in  di- 
rect communication  with  the  enam- 
el spaces,  but  only  mediately,  as 
has  been  described.  These  cavi- 
ties are  filled  with  protoplasmic 
material.  Those  immediately  adjoining  the  cement  are  small 
in  size,  and  form  what  is  known  as  the  granular  layer  of 
Tomes  or  PurJcinje. 

Dentinal  globules  (Fig.  39,  2)  is  the  name  given  to  certain 
spheroidal  masses  that  are  regarded  (Waldeyer)  as  calcified 
remains  of  the  corpuscles  in  the  spaces.  The  contours  of  these 
masses  correspond  in  outline  with  those  of  the  interglobular 
spaces. 


FIG.  39.— Canine  tooth  of  man,  present- 
ing  a  portion  of  the  transverse  section  of 
the  root :  1.  cement  with  larsre  lacunae  and 
parallel  striae ;  2,  interglobular  substance  ; 
8,  dentinal  tubulea.  Magnified  300  diame- 
ters. (Waldeyer.) 


THE    TEETH.  105 

Beneath  the  cement  the  intercommunication  of  interglobu- 
lar  spaces  and  bone-lacunae  is  well  shown.  The  interglobular 
substance  is  apt  to  be  present  in  layers ;  the  lines  which  are 
then  called  the  incremental  lines  of  Salter,  are  supposed  to 
show  that  there  has  been  growth  by  successive  stages.  The 
lines  of  Schreger  (Fig.  38, 2)  are  also  waving  parallel  lines  ;  they 
are  thought  to  be  due  to  the  curvature  of  a  series  of  adjacent 
fibres.  In  some  instances  vascular  channels  have  been  found 
in  the  dentine,  which  has  acquired  the  name  osteo  or  vaso- 
dentine.  In  pathological  conditions  masses  have  also  been 
found  containing  bone-lacurise.  They  have  been  called  odonto- 
mata  by  Yirchow. 

The  cement  is  true  bone-tissue,  containing  lacunae  and 
canaliculi,  and  in  them  the  bone-corpuscles  with  their  pro- 
cesses. The  matrix  is  also  subdivided  into  lamellae.  The  peri- 
osteum of  the  gum  dipping  down  into  the  bony  socket  from 
the  surface  of  the  gum  forms  a  coating  over  the  cement.  Oc- 
casionally Haversian  canals  and  blood-vessels  are  seen  where 
the  cement  is  thick  (Salter).  Sharpey' s  fibres  may  also  be  seen, 
according  to  Waldeyer. 

The  pulp  is  a  substance  that  belongs  to  the  connective- 
tissue  series.  Adjoining  the  dentine  are  two  layers  of  corpus- 
cles. The  nearest  are  long  cylindrical  bodies  whose  oval  nuclei 
are  distant  from  the  dentine.  Wedged  in  between  them,  and 
forming  a  layer  intermediate  between  them  and  the  pulp,  are 
peculiar  branched  corpuscles  of  a  spindle  or  pyramidal  shape. 
According  to  Klein,  these  latter  send  processes  into  the  den- 
tinal  tubules,  while,  according  to  Waldeyer  and  Boll  the  odon- 
toblasts  send  the  fibres,  and  are  also  connected  to  one  another 
by  lateral  processes.  The  pulp  tissue  is  very  rich  in  non- 
medullated  nerves  ;  their  prolongations  penetrate  between  the 
odontoblasts,  but  it  is  a  matter  of  question  whether  they  enter 
the  dentinal  canals. 

Capillaries  are  abundant  and  form  close  networks  in  the 
pulp.  The  lymphatics  are  said  to  accompany  the  blood-vessels 
and  to  be  surrounded  by  endothelial  sheaths. 

Development  of  t?ie  teeth. — Waldeyer,  whose  views  on  the 
teeth  are  the  most  complete  and  satisfactory  extant,  makes  the 
following  succinct  statement : 

"The  anatomical  model  of  a  tooth  of  a  vertebrate  animal 
is  a  large  papilla  of  the  mouth  or  of  the  pharyngeal  mucous 


106 


MANUAL    OF    HISTOLOGY. 


membrane,  which  in  consequence  of  chemical  and  histological 
conversion  of  its  constituents  has  acquired  a  remarkable  degree 
of  hardness,  and  according  to  whether  the  connective- tissue 
substance  of  the  papilla  participates  in  the  hardening  or  not, 
two  large  groups  of  teeth  are  distinguished — dentinal  teeth  and 
horny  teeth.  The  horny  teeth  are  by  far  the  most  simple  in 


FIG.  40.— Vertical  section  of  the  inferior  maxilla  of  a  hu- 
man foetus,  measuring  11  ctms.  from  the  vertex  to  the.  coccyx. 
Magnified  25  diameter?.  1,  dental  groove ;  2,  remains  of  the 
enamel  germ ;  3,  enamel  organ  presenting  externally  epitheli- 
um, as  also  where  it  forms  the  enamel  germ  of  the  papillae  of 
the  dental  sacculus  ;  4,  secondary  enamel  germ  :  rudiment  of 
the  permanent  tooth ;  5,  dental  germ :  6.  lower  jaw ;  7, 
Meckers  cartilage.  (Waldeyer.) 


FIG.  41. — 1,  various  forms  of 
odontoblasts,  with  the  three  kinds 
of  processes ;  2.  three  enamel 
cells,  with  a  few  cells  of  the  stra- 
tum intermedium  attached  ;  3,  an 
enamel  cell,  with  a  hmall  portion 
of  enamel ;  4,  fragments  of  ena- 
mel fibres  from  young  and  soft 
enamel ;  5,  old  '.-namel  fibres  with 
transverse  Ptrias  and  rounded  ex- 
tremities. (Waldeyer.) 


their  structure.  They  appear  as  more  or  less  developed  papil- 
lae covered  with  a  thick  horny  investment.  They  are  never 
continuous  with  portions  of  the  skeleton,  but  constitute  the 
transition  to  other  horny  formations,  as  hairs,  stings,  etc." 

"In  the  dentinal  teeth  the  connective-tissue  matrix  of  the 
papillae  plays  a  most  important  part  in  the  hardening  process, 
which  here  proceeds  in  a  manner  precisely  similar  to  the  ossi- 
fying process,  except  that  no  true  bone  is  formed,  but  only  an 
allied  substance,  of  much  harder  consistence,  and  differing 
more  or  less  in  histological  structure,  termed  dentine.  The  epi- 
thelium of  the  tooth  papillae  either  atrophies  to  a  rudimentary 


THE    TEETH. 


107 


horny  investment — the  cuticula  (membrane  of  the  enamel)— or 
it  becomes  elongated  in  a  remarkable  manner  into  long,  petri- 
fied prisms,  which  collectively  invest  the  dentine  and  are 
known  as  the  enamel." 

Preparations  for  the  development  of  the  teeth  take  place  at 
a  time  when  the  epithelium  of  the  mucous  membrane  of  the 
mouth  is  found  growing  downward,  like  a  solid  peg,  with  a 
rounded  extremity. 

This  has  been  called  the  primary  enamel  organ.  As  a  next 
step,  the  material  which  is  to  give  form  to  the  tooth  pushes 
upward  as  a  papillary  growth,  and  meeting 
the  epithelial  peg,  pushes  in  or  invaginates 
its  rounded  extremity.  This  is  the  tooth 
papilla,  and  as  it  pushes  upward  ihspri- 
mary  enamel  organ  becomes  the  secondary 
enamel  organ,  or  the  enamel  cap.  We  have 
now  two  tissues  which  are  embedded  in  the 
soft  embryonic  substance,  that  happens  at 
this  early  period  to  be  gelatinous.  That 
portion  of  it  immediately  surrounding  the 
papilla  and  cap  is  called  the  tootJi-sac. 

The  papilla,  which  becomes  highly  vas- 
cular, is  covered,  on  its  outer  surface,  by 
the  odontoblasts,  a  layer  of  columnar  epi- 
thelial corpuscles,  which  elongating,  are 
transformed  directly  into  the  dentinal  sub- 
stance at  their  outer  extremity. 

According  to  Kolliker  and  others,  they 
excrete  the  dentine.  The  former  view  seems 
to  have  the  most  weight  of  argument  in  its 
favor,  but  it  seems  less  likely  that  the  odon- 
toblasts both  make  the  matrix  and  send 
fibres  into  the  tubulse.  The  view  of  Klein 
already  given  seems  to  be  preferable,  and  in  conformity  with 
what  we  know  of  other  connective  substances. 

The  separation  of  the  tooth-sac  from  the  mucous  membrane 
is  effected  by  the  gelatinous  tissue,  which,  gradually  closing  in 
the  neck  of  the  sac,  finally  cuts  it  off.  The  epithelium  of  the 
enamel  cap  is  abundant  and  of  various  kinds ;  into  it  push  a 
number  of  papillary  processes  downward  from  the  gelatinous 
tissue.  Later  the  enamel  cap  is  changed  into  three  membranes. 


FIG.  42.— Longitudinal  sec- 
tion of  a  milk  tooth  from  the 
foetal  sheep,  carried  through 
the  margin  of  the  dentine 
pulp  and  adjoining  portion  of 
the  enamel  organ.  Magni- 
fied 200  diameters.  1,  dental 
sacculus;  2,  external  epithe- 
lium and  stratum  interme- 
dium here  united  to  the  in- 
ternal epithelium  or  enamel 
cells ;  3,  after  the  disappear- 
ance of  the  enamel  pulp ;  4, 
young  layer  of  enamel  de- 
tached from  the  enamel  cells ; 

6,  dentine  ;    6,  odontoblasts : 

7,  part  of  the  dentine  pulp. 
(Waldeyer.) 


108  MANUAL    OF   HISTOLOGY. 

The  middle  membrane  is  a  peculiar  cellular  network,  formed 
by  the  transformation  of  the  middle  epithelium  layer  into  a 
network  of  cells,  below  which  there  is  a  deposit  of  a  hyaline 
material.  The  inner  membrane  is  formed  of  cylindrical  epithe- 
lial bodies,  which  are  called  enamel-cells  ;  outside  of  them  are 
one  or  more  layers  of  polygonal  cells  ;  they  form  the  stratum 
intermedium  of  Hannover.  The  outer  membrane  is  composed  of 
several  layers.  Finally,  the  middle  membrane  disappearing,  the 
outer  and  inner  membranes  are  brought  into  close  apposition. 

Development  of  the  enamel. — This  is  formed  by  the  enamel- 
cells  (inner  epithelium,  Kolliker),  presumably  in  the  same 
way  as  the  dentine  by  the  odontoblasts.  There  is  a  direct  con- 
version of  the  outer  extremities  of  the  enamel-bodies  into  en- 
amel. Kolliker,  Hertz,  and  Kollmann,  however,  regard  the 
enamel  as  an  excretion  from  the  enamel-cells.  The  former 
view  appears  the  more  natural,  especially  as  the  enamel-prisms 
are  continuous  with  the  enamel-cells,  having  the  same  form  and 
shape.  The  successive  stages  of  growth,  it  is  believed,  give 
rise  to  the  transverse  markings. 

Whether  or  not,  in  the  interstitial  substance  of  the  enamel, 
there  are  corpuscular  elements  (Boedecker),  is  a  matter  that 
will  require  further  investigation.  The  outer  membrane  even- 
tually gives  rise  to  the  cuticle  covering  the  enamel. 

The  development  of  the  cement  takes  place  precisely  as 
bone  is  produced,  viz.,  from  the  periosteum,  or,  which  is  the 
same  in  this  instance,  from  the  fibrous  tissue  of  the  tooth-sac, 
the  periodontium. 


BIBLIOGRAPHY. 

The  following  systematic  works  and  journal  articles  may  be  consulted  : 
RETZIUS.     Miiller's  Archives.     1837. 
NASMYTH.     Med.-Chir.  Trans.     Vol.  22.     1839. 
KftLLiKER.    Man.  of  Human  Histology.     1853. 
WBNZEL.    Arch.  d.  Heilkunde.    1868. 
HENLE.    Anatomic.     1871. 

STRICKER.     Manual  of  Histology.     Am.  Ed.     1872. 

TOMES.     Manual  of  Dental  Anatomy,  Human  and  Comparative.     Lond.,  1876. 
OWEN.     Comparative  Anat.  and  Phys.  of  Vertebrates.     1866. 
BOEDECKER.     Dental  Cosmos.     XXL,  409— 416.     Phil.,  1879. 
HEITZMANN.     Microscopic  Anat.  of  Human  Teeth.    Med.  Rec.,  N.  Y.,  1879.    XV., 

187. 
KLEIN.    Atlas  of  Histology.     1879—80. 


CHAPTER  IX. 

GENEKAL  HISTOLOGY  OF  THE  NERVOUS  SYSTEM. 

WE  may  gain  a  clear  conception  of  the  nervous  system  in 
its  general  outlines  by  remembering  that  it  consists  essentially 
of  a  series  of  delicate  cords  which,  on  the  one  hand,  proceed 
from  the  nucleated  bodies  of  the  gray  matter,  conveying  voli- 
tional impulses  to  the  periphery  of  the  organism  ;  or,  on  the 
other  hand,  of  sensitive  peripheral  extremities  that  take  up  the 
impression  of  external  objects  and  carry  them  back  to  the  cen- 
tral gray  substance. 

In  either  case  both  the  conducting  cords  and  the  central 
corpuscles  of  the  gray  matter  possess  no  distinctive  differences, 
such  as  may  be  appreciated  by  the  microscope,  while,  on  the 
other  hand,  the  peripheral  termini  appear  under  many  different 
forms,  the  peculiarity  of  ending  being  dependent  in  part  upon 
the  type  of  tissue  in  which  they  are  found,  partly  upon  the 
office  they  have  to  perform,  and  partly  upon  other  causes  that 
are  unknown  to  us.  The  nerve-centres  are  located  in  the  brain, 
spinal  cord,  and  in  the  ganglia  of  the  cerebro-spinal  and  sym- 
pathetic system. 

The  methods  of  nerve- terminations  that  have  been  described 
may  be  briefly  enumerated  here.  They  are  by  (1)  peculiar 
terminal  bodies,  (2)  loops,  (3)  networks,  (4)  end  bulbs,  (5)  proto- 
plasmic bodies  (cells),  (6)  free  or  pointed  extremities. 

Nerve-fibres. — Of  these  there  are  three  kinds  that  have 
distinctive  differences :  1.  The  myelinic  or  medullated  fibres. 
2.  Fibres  of  RemaJc.  3.  Ultimate  fibrils.  Intermediate  forms, 
such  as  have  been  described  by  various  writers,  under  the  names 
of  protoplasmic  processes,  primitive  fasciculi  or  naked  axis- 
cylinders,  varicose  cylinders,  etc.,  will  be  noticed  in  other  con- 
nections. 

Myelinic  fibres. — These  are  also  known  as  the  medullated. 


110  MANUAL    OF   HISTOLOGY. 

To  the  naked  eye  they  appear  white  and  glistening,  and  are 
the  main  constituents  of  the  peripheric  nerves,  though  they 
occur  in  less  number  in  the  sympathetic  and  also  in  the  brain 
and  cord.  Each  fibre  is  made  up  of  three  distinct  parts  :  (a)  a 
central  cylindrical  cord,  the  axis-cylinder,  about  which  is  a  (b) 
coating  of  soft  homogeneous  fatty  material,  called  myeline 
(medulla,  white  substance  of  Schwann),  forming  for  the  axis- 
cylinder  a  sort  of  tubular  sheath,  while  exterior  to  both  is  a 
delicate  membrane  or  envelope  (c\  the  sJieath  of  ScTiwann  or 
primitive  sheath.1  These  fibres  run  a  parallel  unbranching 
course,  except  near  their  termini  or  origin,  and  are  surrounded 
by  a  connective-tissue  coating  of  varying  thickness.  Their 
diameter  varies  also  according  to  their  situation  and  the  degree 
of  their  tension  or  relaxation.  In  the  nerve-trunks  the  average 
diameter  lies  between  -fa  an^  iio-  millimetre.  In  the  brain  they 
are  described  as  having  sometimes  a  diameter  of  -g-J-g- jnilli metre, 
but  it  is  difficult  to  determine  the  presence  of  a  medulla  in  such 
small  fibres. 

To  study  the  properties  of  a  myelinic  nerve,  we  may  take  a 
portion  of  the  sciatic  from  a  frog  that  has  just  been  killed. 
Having  removed  it  with  care  and  placed  it  in  a  drop  of  water 
on  a  slide,  we  should  separate  the  fibres  carefully  with  needles, 
taking  care  not  to  tear  them.  Then  adjusting  a  covering 
glass,  it  will  be  seen  that  from  the  broken  end  of  the  nerve  a 
soft  substance  is  exuding  (Fig.  43,  5) ;  in  a  few  minutes  it  is 
pushed  off  in  the  form  of  drops  of  irregular  shapes  (Fig.  43,  c). 
This  material  is  the  myeline  or  medulla.  It  will  be  seen  to  re- 
fract the  light  strongly,  and  show  concentric  markings.  It  will 
also  be  seen  that  each  fibre  has  a  double  contour  and  is  divided 
at  tolerably  regular  intervals  by  transverse  divisions,  which  are 
now  known  as  Ranmer*  s  nodes.  (See  Fig.  47.)  Midway  be- 
tween each  node  we  may  perhaps  see  an  oval  body  surrounded 
by  a  broad  expansion  of  protoplasm.  In  a  few  fibres  we  may 
even  see  that  a  fine  thread-like  process  is  projecting  from  the 
broken  ends  of  the  nerve-fibre — the  axis-cylinder  (Fig.  43,  d) — 
while  the  whole  fibre  is  enclosed  by  a  delicate  tightly  investing 
membrane,  the  sheath  of  Schwann.  Possibly  we  may  also  see  the 

1  A  most  unfortunate  source  of  confusion  among  histologists  has  arisen  from  the 
use  of  the  word  neurilemma,  which  by  some  is  spoken  of  as  synonymous  with 
Schwann1  s  sheath  (Frey),  and  by  others  as  the  connective  tissue  which  binds  the 
nerve-fibres  together  (Klein,  Rutherford).  We  shall  avoid  the  term  altogether. 


GENERAL    HISTOLOGY    OF   THE    NERVOUS    SYSTEM.         Ill 


oblique  or  arrow  markings  (incisures  of  Schmidt)  (Fig.  43,  /), 
which  seem  first  to  have  been  accurately  described  by  Schmidt, 
of  New  Orleans,  later  by  Lantermann,  of  Cleveland,  Shaw,  and 
others.  The  same  appearances  can  be  also  obtained  by  the  use 
of  iodized  serum. 

The  double  contour  is  not  visible  in  all  the  myelinic  nerves, 
but  is  most  marked  where  they  show  varicose  swellings,  a  con- 
dition that  is  due  to  a  preponder- 
ance of  myeline  at  the  enlarged 
point.  From  this  fact  and  anoth- 
er, that  the  drops  of  myeline  when 
separated  from  the  fibre  show  the 
same  double  contour,  it  is  argued 
that  the  double  marking  in  the 
fibre  is  due  to  a  refracting  (double) 
of  the  myeline,  and  has  nothing  to 
do  with  the  membranous  sheath. 
These  varicosities  just  mentioned 
are  not  to  be  confounded  with  the 
bulgings  of  the  ultimate  fibrils,  or 
with  the  "  necklace  "  appearances 
seen  in  the  course  of  the  fibres  of 
Remak,  both  of  which  latter  may 
probably  be  regarded  as  artificial 
productions,  either  from  stretching 
in  the  act  of  teasing  or  from  the 
imbibition  of  water.  In  the  brain 
of  the  calf  they  are  frequently  seen, 
and  they  are  said  to  be  found  in  the 
intracranial  part  of  the  olfactory, 
optic,  and  acoustic  nerves.  The 
fibres  in  which  this  change  occurs 
are  usually  quite  small. 

Staining    in  picro-carmine. — 

This  reagent  has  been  recommended  by  Ranvier.  It  is  satis- 
factorily prepared  by  Rutherford's  process.1  Taking  precau- 
tions not  to  injure  the  nerve  in  removing  it,  mount  in  the  solu- 

1  He  takes  100  c.c.  of  a  saturated  solution  of  picric  acid.  Next  he  prepares  an 
ammoniacal  solution  of  carmine  by  dissolving  one  gramme  in  a  few  c,  c.  of  water, 
with  the  aid  of  an  excess  of  ammonia  and  heat.  He  then  boils  the  picric  acid  solu- 
tion on  a  sand-bath,  and  when  boiling  adds  the  carmine  solution.  The  mixture  is 


Fio.  43.— a,  Myelinic  fibre  in  a  state  of 
"  coagulation  ;  "  &,  myeline  exuding  from 
the  broken  end  of  the  fibre ;  c,  drops  of  mye- 
line separated  from  the  nerve-fibre  ;  rf,  axis 
cylinder ;  <?,  nucleus  of  Henle's  sheath ;  /, 
arrow  markings. 


112 


MANUAL    OF   HISTOLOGY. 


tion.  The  nuclei  will  then  be  stained  a  brick-red,  while  the 
sheath  of  Schwann,  and,  in  fact,  the  whole  nerve,  will  be  stained 
yellow.  It  is  said  that,  if  the  axis-cylinder  projects,  it  will  be 
stained  a  bright  red,  though  twenty-four  hours  may  be  required 
to  effect  the  staining.  In  my  hands  picro-carmine  has  not 
proved  so  successful  a  coloring  agent  as  some  others. 

Staining  witJi  the  nitrate  of  silver. — The  sciatic  or  any 
peripheral  nerve  may  be  employed.  Expose  it  without  re- 
moval in  a  frog  that  has  just  been  killed.  Then  dry  up  all 
fluid  from  about  it,  and  pour  on  a  solution  of  the  nitrate  (1  to 
1,000).  In  this  way  the  nerve-fibres  will  be  made  rigid.  They 
are  then  to  be  removed  with  a  pair  of  delicate  scissors,  and 
placed  in  a  flat  vessel  containing  a  little  more  of  the  solution. 
After  a  few  minutes  the  nerve  will  look  turbid,  and  then  it 
should  be  cut  out  and  washed  in  distilled  water,  and  exposed 
to  the  sunlight.  In  a  variable  time  (ten  to  fifteen  minutes)  the 
turbid  appearance  will  give  way  to  a  brown  coloration.  Exam- 
ining a  single  funicu- 
lus  or  bundle  in  gly- 
cerine, it  will  be  seen 
that  it  has  an  endothe- 
lial  coating  of  one  or 
more  layers  (Fig.  44). 

If  another  f  uniculus 
be  separated  with  fine 
needles,1  the  same  care 
being  taken  to  spread 
the  fibres  apart  and  not 
tease,  and  so  lacerate 
them,  it  will  be  seen 
that  each  fibre  con- 
tains a  series  of  Latin 

crosses  at  certain  pretty  regular  intervals.  The  transverse  bar 
of  the  cross  corresponds  to  the  " annular  constriction"  seen 
in  Ranvier's  node,  while  the  axis-cylinder  forms  the  longitudi- 
nal bar.  Close  observation  with  high  powers  will  show  that 
this  latter  is  marked  by  transverse  lines  of  a  dark  brown  or 

then  evaporated  to  dryness,  the  residue  dissolved  in  100  c.c.  of  water,  and  filtered. 
If  the  solution  is  not  clear,  he  adds  more  ammonia,  evaporates,  and  then  dissolves  as 
before. 

1  Milliners7  are  the  best. 


FIG.  44. — Fnniculns  or  Nerve  Bundle  covered  with  Endothe- 
lium  (Epithelium).  From  the  sciatic  of  the  frog.— Hartnack, 
object.  4,  oc.  2. 


GENERAL    HISTOLOGY    OF   THE    NERVOUS    SYSTEM.         113 

black  (Frommanrfs  lines).  It  appears  probable,  as  Ranvier 
explains,  that,  owing  to  the  break  in  the  myeline,  at  the  *c  an- 
nular constriction,"  the  particles  of  silver  gain  an  entrance  to 
the  axis-cylinder  at  this  the  only  unprotected  spot.  If  the 
action  of  the  salt  is  long  con- 
tinued, the  axis-cylinder  is  col- 
ored for  a  somewhat  longer 
distance.  The  transverse  bar 
seems  to  be  formed  of  two 
conical  segments  set  base  to 
base.  The  position  of  this  bi- 
conical  segment  usually  cor- 
responds in  position  with  the 
"annular  constriction,"  but 

i t  won  1  rl  n  rmpa v  fh a  f  fh PV  m n  v  FlG'  45<~a'  Ranvier's  disk  5  &'  Frommann's lines ; 
11  WOUld  clppedT  tlldt  tliey  nitty  c,  nucleus  of  interannular  segment. 

be   separated,  for,   when   the 

tissue  of  the  nerve  has  been  put  upon  the  stretch,  the  biconical 
segment  may  be  drawn  away  from  the  annular  constriction. 
(See  Fig.  45.) 

Now,  as  Schwann's  sheath  is  understood  to  end  at  the  an- 
nular constriction,  where  it  is  cemented  to  the  next  adjoining 
segment  just  as  epithelial  cells  are  joined  together,  the  biconi- 
cal disk  may  belong  to  the  axis-cylinder  exclusively,  and 
merely  constitute  a  dividing  line  between  its  segments.  Ac- 
cording to  Engelmann,  the  axis-cylinder  is  divided  up  into 
portions  corresponding  with  the  interannular  segments. 

According  to  Bawitz,  Schwann's  sheath  does  not  end  at  the  nodes,  but  is 
continuous  with  the  sheath  of  the  adjacent  interannular  segment. 

Staining  of  the  nerve  in  osmic  acid — semi-desiccation. — 
Osmic  acid  is  one  of  the  most  valuable  reagents  for  histological 
work,  and  the  method  now  to  be  described  (a  modification  of 
KanvierV)  succeeds  well.  Take  the  frog's  sciatic,  or  any  other 
peripheral  nerve,  carefully  remove  a  portion  with  the  surround- 
ing tissue,  keep  the  whole  extended  with  pins,  upon  a  flat  bit 
of  cork,  and  then  dip  it  into  a  vessel  containing  a  1  per  cent, 
watery  solution  of  osmic  acid.2  The  vessel  is  then  to  be  exposed 
to  the  light.  The  whole  nerve  will  be  more  or  less  thoroughly 

1  Lemons  sur  1'Histologie  du  Systeme  Nerveux,  Paris,  1878. 

a  The  solution  should,  of  course,  have  been  kept  in  a  dark  bottle  away  from  the 
light. 


114 


MANUAL    OF    HISTOLOGY. 


6.-. 


stained  in  a  few  hours.  The  external  portions,  however,  will 
be  stained  in  a  few  minutes,  and  they  may  be  removed  by  care- 
ful separation  with  fine  needles.  To  mount,  take  a  glass  slide 
and  slip  it  under  the  nerve-fibres,  while  the  needle  is  employed 
to  carry  them  up  on  to  a  dry  part  of  the  slide 
where  they  can  be  placed  side  by  side.  Then 
remove  the  excess  of  water  with  bibulous  paper, 
and  let  the  fibres  get  so  dry  that  they  adhere 
to  the  slide.  Place  about  them  a  ring  of  tis- 
sue-paper, so  that  when  the  cover  is  adjusted 
it  will  not  press  upon  the  fibres.  Fix  the  cover 
at  different  points  with  paraffine,  then  put  a 
drop  of  glycerine  upon  one  side,  and  a  drop  of 
water  upon  the  other.  The  union  of  water  and 
glycerine  should  be  allowed  to  go  on  for 
twenty-four  hours  in  a  damp  place.  The  con- 
strictions and  arrow-markings  are  usually  well 
seen.  The  nuclei  also  are  occasionally  to  be 
found  in  a  niche  of  the  myeline.  These  bodies, 
however,  are  better  seen  in  specimens  that  have 
been  a  short  time  (fifteen  or  twenty  minutes) 
in  osmic  acid,  and  then  in  picro-carmine  a  few 
hours.  It  still  is  a  question  among  histologists 
whether  the  arrow-markings  are  artificial  or 
not ;  each  of  the  sections  lying  between  the 
markings  is  called  the  cylindro-conical  segment 
(Hohlcylinder,  Kuhnt).  (See  Fig.  43.) 

Transverse  sections  of  myelinic  'nerves. — 
Certain  points  are  best  seen  by  making  trans- 
verse sections.  Prepare  the  sciatic  of  a  frog  or 
any  of  the  human  peripheral  nerves  by  im- 
mersing a  few  days  in  a  sherry-colored  solution 
of  bichromate  of  potash,  or  in  Mueller' s  fluid, * 
and  then  in  90  per  cent,  of  alcohol,  until  the  tis- 
sue is  hard  enough  to  cut.  Then  it  is  to  be 
mounted  in  the  microtome  with  wax  and  oil  of 
about  its  own  consistence.  Sections  are  to  be  made  with  the 
razor;  or  it  may  be  mounted  in  elder-pith  in  the  following 
way  :  bore  out  from  the  centre  of  the  pith-cylinder  a  cylindri- 

1  The  well-known  eye-fluid,  of  which  the  composition  is  :  Bichromate  of  potash, 
2  to  2£  grammes ;  sulphate  of  soda,  1  gramme ;  distilled  water,  100  grammes. 


FIG.  46.  —  Human 
myelinic  nerve  :  a,  In- 
terannular  segment ;  &, 
Ranvier's  node  ;  c.  nu- 
cleus of  the  interannu- 
lar  segment  surround- 
ed by  granular  proto- 
plasm; rf,  Henle's 
sheath  with  nucleus. 


GENERAL    HISTOLOGY    OF   THE    NERVOUS    SYSTEM.         115 

cal  liole  a  little  larger  than  the  trunk  of  the  nerve,  then  im- 
merse the  whole  in  water,  and  the  pith  will  begin  to  swell.  As 
soon  as  it  has  firmly  embraced  the  nerve,  sections  may  be 
made  with  the  knife.  Ammonia-carmine  will  stain  the  axis- 
cylinder  well,  but  the  outline  of  the  cut  will  appear  irregular 
rather  than  round.  This  appearance  is  doubtless  artificial.  In 
my  hands,  borax-carmine  l  has  proved  much  better  than  the 
ammonia-carmine,  as  it  diffuses  very  little,  and  much  of  the 
excess  may  be  removed  by  dilute  acetic  acid  (about  J  per  cent.), 
in  which  the  specimen  should  remain,  from  a  few  seconds  to  a 
minute  or  two,  until  it  has  become  bright  to  the  eye.  The  fur- 
ther steps  in  the  process  of  making  a  permanent  preparation 
are  the  same  as  those  for  other  specimens;  i.e.,  it  may  be 
mounted  in  glycerine  and  water,  or  clarified  by  clove-oil  and 
mounted  in  dammar  varnish  or  Canada  balsam. 

Preparation  ~by  the  bichromate  of  ammonia. — Ranvier  em- 
ploys of  this  a  2  per  cent,  solution,  allowing  the  specimen  to 
remain,  with  frequent  changes  of  the 
fluid,  from  two  or  three  months  to  a 
year.    The  sections  are  to  be  stained 
in  ammonia-carmine  or  picro-carmine. 
and   mounted  in   glycerine.     It   will 
then  be  seen  that  immediately  about 
the  axis-cylinder  is  a  sheath.    This  is 
called  by  Ranvier  the  sTieath  of  MautJi- 
ner,  from  the  author  who  described  it. 
(See  Fig.  46,  b.)    Specimens  prepared 
in  the  ordinary  way,  by  long  immer-        -*8*-* 
sion  in  Mueller's  fluid  alone,  or  sub- 
sequently in  the  chromic  acid  solution  (gr.  ij. —  1  j.)  and  stained 
with  ammonia-carmine,  occasionally  show  the  same  thing. 

Sometimes  histologists  find  that  embedding  in  gum  succeeds 
best  in  securing  these  transverse  sections  of  nerves.  The  diffi- 
culty of  the  task  is  one  of  considerable  moment.  The  method 
is  as  follows  :  Take  a  fresh  nerve,  harden  it  in  osmic  acid  (1  per 
cent.,  if  it  is  desirable  to  expedite  the  process,  or  TV  per  cent, 
if  it  is  not  necessary  to  conclude  the  examination  the  same 
day).  Then,  when  the  nerve  is  thoroughly  blackened  all  through, 

1  The  powder  is  prepared  by  Eimer  &  Amend,  of  this  city  (205  to  211  Third 
Avenue),  according1  to  Arnold's  formula.  The  strength  required  is>  gr.  xv. —  §  j. 
distilled  water. 


116  MANUAL    OF   HISTOLOGY. 

it  is  to  be  immersed  in  water  for  a  few  hours  ;  then  in  90  per 
cent,  alcohol,  and  then  in  a  weak  solution  of  gum-arabic, 
which  fills  the  interstices  between  the  bundles,  and  finally  in 
strong  alcohol  (95  per  cent.),  which  hardens  the  gum  sufficiently. 
The  sections,  cut  as  thin  as  possible,  should  be  placed  on  a 
slide  to  remove  the  excess  of  alcohol,  which  may  be  done  with 
filter-paper.  A  drop  of  water  is  then  to  be  added ;  about 
the  cover  put  a  few  drops  of  carbolized  water  ;  remove  to  a 
damp  place.  At  the  end  of  twenty -four  hours  the  gum  will 
have  dissolved,  and  then  the  glycerine  may  be  allowed  to  enter 
slowly  without  displacing  the  elements  (Ranvier). 

In  examining  such  cross-sections,  the  medullated  nerves  will 
present  various  diameters,  and  the  contour  of  the  myelinic 
sheath  will  vary  in  width  and  outline  according  as  the  cut 
comes  through  the  broadest  part  of  the  arrow-marking,  or 
through  the  thin  overlapping  parts.  (See  Fig.  43.)  If  the  cut 
chances  to  pass  close  to  the  annular  constriction,  no  myeline 
will  of  course  be  seen.  For  these  reasons,  the  cross-sections  of 
such  nerves,  when  stained  with  osmic  acid,  are  very  different. 

Modern  conceptions  of  myelinic  nerves. — The  specimens 
that  have  been  studied  according  to  the  methods  given  will  not 
have  shown  any  termination  of  the  nerves,  or  any  division, 
either  into  trunks  of  any  considerable  size  or  into  the  fibrils  of 
which  they  are  said  to  be  composed.  They  do,  however,  as  we 
have  already  said,  divide  both  near  their  origin  and  near  their 
termination.  It  is  presumed  that  each  fibril  of  which  the  axis- 
cylinder  is  composed  passes  directly  through  from  its  point  of 
origin  of  the  nerve-centres,  to  its  final  point  of  distribution, 
without  branching.  It  is  difficult,  however,  with  the  instru- 
ments in  ordinary  use,  to  see  any  distinct  marks  of  fibrillation 
in  cross-sections  of  the  axis- cylinder,  and  it  is  in  them  that  we 
should  expect  to  see  them  best.  The  ideas  pf  Ranvier  are  well 
worthy  of  consideration,  as  he  has  given  more  form  and  solid- 
ity to  our  conception  of  the  intimate  structure  of  a  myelinic 
nerve-fibre  than  any  previous  writer.  According  to  him,  each 
section  of  nerve  between  the  annular  constrictions  represents 
an  ultimate  morphological  element.  It  is,  in  fact,  a  tubular 
cell,  whose  proper  external  portion  (the  membrane  of  the  cell, 
according  to  common  phraseology)  is  the  sheath  of  Schwann, 
while  the  myeline  or  medulla  fills  the  interior,  just  as  in  adi- 
pose tissue  a  globule  of  oil  fills  out  and  distends  an  ordinary 


GENERAL    HISTOLOGY    OF   THE    NERVOUS    SYSTEM.         117 

connective- tissue  corpuscle.  Each  of  these  bodies,  which  he 
calls  an  interannular  segment,  begins  and  ends  at  the  constric- 
tion. It  contains  a  single  ovoid  flattened  nucleus,  which  fills 
a  niche  in  the  myeline,  and  is  surrounded  by  a  broad,  thin  ex- 
pansion of  protoplasm  (the  body  of  the  corpuscle).  The  axis- 
cylinder  has  nothing  to  do  with  this  body  that  we  have  de- 
scribed, except  that  it  pierces  it.  Instead  of  stopping  short  at 
each  constriction,  it  goes  on  indefinitely.  As  we  have  already 
seen,  the  annular  constriction  and  the  biconical  disk  are  not 
always  at  the  same  point,  which  argues  strongly  for  Ranvier's 
views.  The  myelinic  sheath  probably  protects  the  delicate 
fibre  from  external  injury,  but  whether  it  also  insulates  it,  is 
problematical.  In  the  foetus  all  nerves  are  devoid  of  myeline. 

Fibres  of  Remak. — These  are  called  by  some  the  amyelinic 
or  non-medullated  fibres,  by  others  the  pale,  gray,  or  gelati- 
nous fibres.  The  term  Remak' s  fibres  has  come  into  use  re- 
cently as  the  distinctive  name  for  certain  nerve-fibres  abound- 
ing in  the  sympathetic,  as  distinguished  from  others  which 
also  contain  no  myeline,  and  are  found  in  the  cranial  portions 
of  the  optic,  auditory,  and  olfactory  nerves.  Each  fibre  is 
marked  with  oval  nuclei  at  pretty  short  intervals,  and  has  an 
indistinct  longitudinal  striation,  probably  the  evidence  of  fibrils 
such  as  are  believed  to  exist  in  the  axis-cylinder.  The  nuclei 
are  imbedded  in  a  homogeneous  sheath.  There  being  no  breaks 
in  the  continuity  of  the  fibre,  there  can  be  no  sheath  of  Schwann 
in  the  sense  that  has  been  described.  In  diameter  each  fibre  va- 
ries between  -fa  and  Ti7  millimetre.  In  1838  Remak  first  called 
attention  to  them,  but  his  views  were  received  with  disfavor. 
More  recently,  Max  Schultze,  Frey,  Leydig,  and  Henle  have 
joined  in  representing  them  as  long,  cylindrical,  continuous, 
slightly  striated,  and  dotted  with  nuclei. 

The  fibres  of  Remak  are  found  in  great  abundance  in  all 
the  nerves  of  the  organic  system,  but  they  also  exist  in  all  the 
mixed  nerves,  varying  with  the  kind  of  nerve  and  the  animal. 
They  are  not  found  in  special  nerves.  The  pneumogastric  of  the 
cat  is  well  adapted  for  the  study  of  them,  as  the  myelinic  fibres 
are  present  in  considerable  quantity,  and  make  the  mechanical 
separation  of  the  bundle  easy.  Associated  with  them,  fibres  are 
often  seen,  that  are  shown  in  Fig.  48,  c.  They  are  delicate, 
run  a  wavy  course,  and  sometimes  exhibit  curious  varicosities 
(a),  (necklace  appearance).  The  nuclei  are  placed  at  about  the 


118 


MANUAL    OF    HISTOLOGY. 


same  distances  apart  as  in  the  other  form  of  fibre  already  men- 
tioned. 

Preparation  in  osmic  acid  and  pier o-car mine. — Remove 
the  pneumogastric  in  the  following  way,  from  a  cat  that  has 
just  been  killed :  Having  exposed  the  nerve,  slip  under  it  in 
situ  a  long  narrow  strip  of  cork,  to  which,  pin  down  the  nerve 
with  some  adjacent  tissue,  all  of  which  may  be  removed  at 

once  and  placed  in  a  solution 
of  osmic  acid  (1—1,000)  for 
twenty -four  hours  ;  the  nerve 
may  then  be  separated  from 
its  attachments  and  placed 
in  the  picro-carmine  solution 
for  still  another  twenty -four 
hours.  The  excess  of  the  col- 
oring agent  may  be  removed 
by  dipping  for  a  few  seconds 
in  acetic-acid  solution  (J-  per 
cent.),  and  then  the  nerve 
may  be  placed  in  alcohol, 
afterwards  in  water,  and  fin- 
ally mounted  in  glycerine. 
It  will  be  seen  that  the  nerve- 
fibres  are  stained  a  reddish 
yellow,  while  the  nuclei  are 
brick-red.  The  picric-acid 
yellow  is  apt,  however,  to 
diffuse.  Careful  separation 
of  the  fibres  may  show  that 
they  branch,  as  shown  in  Fig. 
48,  A,  B ;  and  yet  this  char- 
acteristic, which  Eanvier  in- 
sists upon,  is  by  no  means 
easy  to  see  in  most  of  the  fibres,  in  fact  it  requires  much  care- 
ful work  before  it  is  apparent.  The  myelinic  nerves  will  be  dis- 
tinguished by  their  greater  average  size,  their  dusky,  granular 
medulla,  broken  at  points,  and  by  the  axis-cylinder,  which, 
if  it  does  not  project,  may  be  seen  winding  spirally  along  be- 
neath its  medullary  coat.  In  them,  too,  as  a  rule,  each  in- 
terannular  segment  contains  but  one  nucleus. 

Preparation  of  Remak"1  s  fibres  in  hcematoxylin. — One  of 


FIG.  48.— Fibres  of  Remak.  A,  Pneumogastric 
of  the  cat— haeiuatoxylin  specimen  :  a,  nerve  nu- 
clei ;  &,  appearances  of  branching ;  c,  connective- 
tissue  sheath.  B,  Same.  Picro-carmine  specimen. 
The  branching  in  this  case  is  more  evident.  C, 
Same — haematoxylin  specimen.  The  necklace  ap- 
pearance is  >shown  at  a. 


GENERAL    HISTOLOGY^  OF    THE    NERVOUS    SYSTEM.         119 

the  most  rapid  and  successful  methods  is  by  the  use  of  hsema- 
toxylin.  The  pneumogastric  nerve  of  a  cat  is  removed  and 
immediately  placed  in  the  hsematoxylin  solution  ;  then,  after 
thorough  staining,  which  may  only  take  a  few  minutes,  in 
dilute  acetic  acid  (^  per  cent.),  and  finally  mounted  in  gly- 
cerine. In  this  way  the  nuclei  will  be  stained  a  beautiful  pur- 
ple, while  the  fibres  will  be  unaffected.  The  number  of  nuclei 
and  absence  of  medulla  will  serve  to  distinguish  the  fibres  of 
Eemak  from  the  medullated.  It  is  difficult  by  any  method  of 
preparation  to  see  that  there  are  any  precise  limits  to  the  lon- 
gitudinal lines  in  the  fibres,  i.e.,  that  the  striation  is  due  to 
little,  short,  narrow  rods,  lying  side  by  side  (Ranvier).  The 
nitrate  of  silver  demonstrates  no  transverse  markings  and  no 
constrictions  or  crosses.  There  is  but  little  likelihood  in  these 
specimens  to  mistake  the  fibres  for  connective- tissue  bundles. 
In  the  first  place,  the  nuclei,  and  what  cell-bodies  happen  to 
be  about  them,  of  the  one,  are  small,  flattened,  ovoid  bodies 
occurring  at  pretty  regular  intervals,  while  the  connective-tis- 
sue corpuscles  are  usually  larger,  longer,  and,  though  they 
may  appear  oat- shaped,  when  the  side  is  turned  to  the  observer, 
are  broad  plates  with  irregular  edges  when  seen  flatwise.  In 
the  second  place,  the  fibres  run  their  course  in  long,  narrow 
bundles,  as  no  connective  tissue  does. 

Ganglionio  bodies. — Of  these  there  are  three  kinds :  1. 
Those  that  are  connected  with  the  spinal  and  some  cerebral 
nerves.  2.  Those  found  in  the  gray  substance  of  the  brain  and 
spinal  cord.  3.  Those  in  the  ganglia  of  the  sympathetic  sys- 
tem. These  bodies  are  of  such  large  size  that  they  may  often 
be  seen  with  the  naked  eye.  In  the  human  species  they  are 
usually  in  close  connection  with  the  origin  of  the  nerves,  though 
they  also  may  be  interspersed  at  points  through  the  course  of 
the  fibres  or  may  be  present  near  their  points  of  distribution 
(ganglia  of  AuerbacTi).  Their  immediate  connection  with  the 
nerve-fibre  is  made  in  the  following  ways  :  1.  A  large  process, 
which  does  not  at  first  appear  to  branch,  passes  off,  and  is 
continuous  with  the  axis- cylinder.  2.  Fine  branches  are  given 
off  from  one  or  more  corpuscles,  and,  uniting,  contrive  to  form 
a  nerve-fibre  (either  a  fibre  of  Eemak  or  a  myelinic  fibre).  3. 
These  branches  after  combination  may  pass  through  a  gangli- 
onic  corpuscle,  which  then  is  called  bipolar  (Gerlach,  Wal- 
deyer).  In  the  sympathetic  system  we  have  the  unbranched 


120  MANUAL    OF   HISTOLOGY. 

process  and  the  superficial  or  spiral  fibre,  which  corresponds  to 
the  branched  fibre  of  the  ganglionic  bodies  of  the  brain  and 
spinal  nerves. 

Ganglia  of  the  cranial  and  spinal  nerves. — These  organs, 
which  appear  to  the  naked  eye  as  nodular  enlargements  of  the 
nerves  with  which  they  are  connected,  consist  of  groups  of 
peculiar  large  corpuscles  which  are  interspersed  among  the 
nerve-fibres.  In  shape  they  are  usually  large  and  ovoid,  or 
pear-shaped.  About  and  between  them  are  bands  of  connective 
tissue  studded  with  nuclei,  forming  for  each  separate  body  a 
kind  of  capsule  ;  the  vascular  supply  to  them  is  liberal.  The 
contents  of  these  bodies  are  soft,  elastic,  and  beset  with  gran- 
ules. They  have  a  large,  globular,  or  ovoid  nucleus  or  nucleo- 
las,  and  may  appear  to  have  no  process,  or  to  be  unipolar  or 
bipolar,  as  in  the  lower  animals.1 

Examination  of  the  Gasserian  ganglion  in  ihe  frog. — 
Take  a  frog  that  has  just  been  killed,  or,  better  still,  one  that 
has  been  some  time  in  Mueller' s  fluid ;  trace  the  fifth  nerve 
into  the  skull.  On  it  will  be  seen,  just  within  the  bone,  a  yel- 
low enlargement.  This  is  to  be  removed  with  forceps  and 
teased  with  needles.  The  ganglionic  bodies  usually  appear  to 
have  no  processes  (apolar),  but  they  probably  have  one  or  more, 
and  the  apparent  absence  of  them  is  because  they  have  been 
torn  off  in  teasing. 

Examination  of  the  ganglia  of  the  spinal  cord. — Take  the 
cord  of  a  bullock,  and  prepare  it  while  fresh,  or  after  it  has 
been  a  greater  or  less  time  in  Mueller' s  fluid,  or  a  weak  so- 
lution of  the  bichromate  of  potash  (gr.  xv. —  %  j.).  Having  cut 
it  into  transverse  segments,  the  gray  substance  may  be  easily 
seen.  Snip  out  with  fine  curved  scissors  small  pieces  from  the 
anterior  horns  in  the  lumbar  regions  where  the  corpuscles  are 
very  numerous  ;  if  the  specimen  be  fresh,  immerse  in  osmic 
acid  (1 — 1,000)  for  twenty-four  hours.  Then,  by  careful  brush- 
ing in  water  with  the  camel' s-hair  brush,  or  by  teasing,  or  agi- 
tation in  a  test-tube  with  a  little  distilled  water,  some  of  the 
ganglionic  corpuscles  will  be  successfully  removed.  They  will 
be  seen  to  vary  much  in  size,  and  be  multipolar,  i.e.,  they  will 
exhibit  a  very  large  number  of  branches  (Deiter' s  protoplasmic 


1  According  to  Key  and  Retzius,  they  are  probably  all  unipolar.     Stud,  in  der 
Anat.  d.  Nerven-Syst.,  2  Hiilfte,  V.  and  H.'s  Jahresb.,  1878. 


GENEKAL   HISTOLOGY    OF   THE    NERVOUS    SYSTEM.         121 

processes)  which  divide  and  subdivide,  and,  it  is  said,  form  a 
network  which  unites  with  a  similar  one  proceeding  from  the 
ganglionic  bodies  of  the  posterior  roots. 

There  is,  in  addition,  a  single  straight  process  (naked  axis- 
cylinder),  which,  proceeding  outward,  soon  receives  a  medul- 
lary sheath.  The  nucleus  is  very  large  and  circular,  and  usu- 
ally displays  a  nucleolus.  The  contents  of  the  body  of  the 
corpuscles  are  more  or  less  granular,  and  a  mass  of  pigment  in 
granules  is  usually  seen  piled  up  in  some  one  portion.  The 
corpuscles  thus  separated  may  be  preserved  in  glycerine  and 
water,  or,  after  staining  in  borax-carmine,  in  dammar  varnish 
or  Canada  balsam.  In  the  posterior  horns  the  corpuscles  are 
similar  in  character,  but  smaller.  Gerlach  claims  that  the 
ganglionic  bodies  of  the  anterior  horns  are  connected  together 
through  networks  formed  of  the  branching  processes  given  off 
from  each.  Carriere,  working  under  Prof.  Kollman,  of  Mu- 
nich, has  examined  the  spinal  cord  of  the  calf  in  the  fresh  con- 
dition, and  has  satisfied  himself  that  the  ganglionic  corpuscles 
are  connected  together  by  their  fine  processes,  being  thus  in 
agreement  with  Stilling,  Wagner,  Remak,  and  many  others. — 
ArcTi.f.  mikroskop.  Anat.^  xiv.,  2,  1877. 

Ganglionic  bodies  in  the  human  'brain. — Thin  sections 
made  through  the  cortex  of  the  human  brain  show  that  there 
are  conical  ganglionic  corpuscles  of  medium  size,  whose  base 
is  directed  toward  the  white  substance,  and  apex  toward  the 
superficies.  From  either  end  processes  are  given  off,  from  the 
broad  end  several,  and  from  the  apex  a  single  one ;  both  subse- 
quently branch.  In  the  upper  strata  the  corpuscles  are  small- 
est. Disseminated  throughout  this  substance  are  two  other 
forms  of  corpuscles,  one  star-shaped  (spider-cells),1  and  the 
other  the  lymphoid  corpuscles  that  belong  to  all  tissues  of  the 
body.  Possibly  the  spider-cells,  which  have  a  variable  number 
of  processes,  are  the  cells  of  the  neuroglia.  Brush-cells 2  have 
also  been  described.  Perhaps  they  should  also  be  regarded  as 
a  variety  of  the  spider-cells. 

Ganglionic  bodies  of  the  sympathetic  system. — They  occur 
either  singly  or  in  groups,  interspersed  among  the  nerve-fibres, 
or  in  lines,  or  form  enlargements  in  the  nerve-plexuses,  as 

1  Described  by  Jastrowitz. 

3  Arch.  f.  mikrosk.  Anat,  1874,  LXI.,  p.  93. 


122  MANUAL    OF   HISTOLOGY. 

in  the  digestive  tract.  Preparations  of  the  cceliac  ganglion  of 
the  frog  may  be  made  according  to  the  methods  that  have  al- 
ready been  described.  The  aorta  and  bulbus  arteriosus  of  the 
frog  are  recommended  by  Klein,  and  the  gold  method  is  the  best 
to  show  them.  It  was  in  these  corpuscles  of  the  green  tree-frog 
that  Beale  noticed  a  spiral  fibre.  It  was  a  delicate  one,  wind- 
ing round  the  axis-cylinder,  finally  going  off  in  an  opposite 
direction.  He  also  thought,  from  an  examination  of  the  gan- 
glia in  the  mammalia,  that  the  same  fibre  existed  in  them.  Sub- 
sequently Julius  Arnold  corroborated  his  views,  and  even  de- 
scribed a  network  of  fibres  which  was  connected  with  the 
nucleolus,  and  extended  through  the  corpuscle,  at  its  final 
exit  forming  the  spinal  fibre.  Recent  observers,  however,  have 
failed  to  confirm  Arnold's  opinion,  and  even  the  existence  of  a 
spiral  fibre  is  held  to  be  in  doubt.1  These  corpuscles,  which  are 
either  globular  or  oblong,  may  appear  to  be  apolar,  unipolar, 
bipolar  (when  two  processes  are  given  off  in  the  opposite  direc- 
tions), or  multipolar  (when  two  are  given  off  in  the  same  direc- 
tion, or  several  are  given  off  in  various  directions). 

Meissnef  s  plexus. — This  network,  named  after  its  dis- 
coverer, is  situated  in  the  submucous  tissue,  and  consists  of 
nerve-bundles  of  medium  size,  which  have  nodular  enlarge- 
ments studded  with  nuclei  at  certain  points.  An  excellent 
way  of  securing  them  is  the  following  :  Take  a  piece  of  cat's 
intestine,  three  or  four  inches  in  length ;  cleanse  thoroughly 
by  passing  through  it  a  stream  of  water ;  then  ligate  one  ex- 
tremity. Fill  an  ordinary  two-ounce  syringe  with  a  solution  of 
the  chloride  of  gold  (£°).  Slip  the  nozzle  into  the  other  end  of 
the  intestine,  and,  tying  it  in,  inject  with  such  force  as  to  dis- 
tend the  gut  to  its  utmost  extent  without  bursting.  Then  pass 
another  ligature  round  the  gut  beyond  the  nozzle,  and  draw  it 
tight.  Remove  the  syringe,  and  place  the  specimen  in  an  open 
vessel  containing  the  same  solution,  but  allowing  fully  one- 
half  of  it  to  be  uncovered  by  the  liquid.  After  twenty -four 
hours  the  part  thus  exposed  will  have  taken  a  mauve  or  violet 
color.  Then  remove  from  the  liquid,  and  open  with  scissors, 
let  it  partly  dry,  and,  seizing  the  mucous  membrane  with  the 
forceps,  tear  it  off  in  pieces.  The  submucous  tissue  will  then 

1  Key  and  Retzius  did  not  find  the  spiral  fibre  in  the  human  species,  but  in  the 
frog  occasionally.  Op.  cit.  Many  other  excellent  observers  agree  with  them. 


GENERAL    HISTOLOGY    OF   THE    NERVOUS    SYSTEM.         123 

be  exposed,  and  small  bits  are  to  be  torn  out  in  a  similar  way. 
They  may  be  mounted  in  glycerine  or  dammar  varnish.  The 
nerve-trunks  can  be  readily  seen ;  they  will  contain,  on  an 
average,  from  two  to  three  fibres  perhaps,  and  form  a  large- 
meshed  plexus.  The  ganglionic  enlargement  may  be  found 
where  three  or  four  bundles  meet,  or  in  the  course  of  a  single 
bundle.  The  diameter  of  the  enlargement  is  three  to  five  times 
the  size  of  the  bundle. 

AuerbacJi's  plexus,  called  after  its  discoverer,  is  seen  by 
taking  the  same  specimen,  and  tearing  out  thin  laminse  from 
the  muscle,  at  the  junction  of  their  longitudinal  and  trans- 
verse coats.  The  ganglionic  bodies  are  nodular,  and  contain 
numerous  nuclei.  It  is  said  that  they  may  be  isolated  by 
immersion  of  the  muscular  tissue  eight  to  ten  days  in  a  10  per 
cent,  solution  of  common  salt.  •  Guinea-pigs  furnish  the  best 
specimens.1  There  are  both  coarse  and  fine  networks. 

Termination  of  nerves. — There  are  various  methods  which 
have  been  described,  and  these  are  :  1,  by  undivided  or  free 
endings  (tendons,  conjunctiva) ;  2,  by  end  bulbs  (cornea) ;  3, 
by  terminal  loops  ;  4,  in  corpuscles  (seminal  canals — Letzerich) ; 
5,  by  networks  (peritoneum) ;  or,  finally,  6,  in  a  special  appa- 
ratus (Pacinian  or  Meissner's  corpuscles).  When  nerves  termi- 
nate by  networks,  the  meshes  may  be  formed  from  the  medul- 
lated  fibres,  or  those  of  Remak,  and  may  consist  of  one  or  more 
fine  fibrils.  They  have  been  found  in  the  skin,  and  are  to  be 
seen  in  the  submucous  tissue  of  the  intestines,  in  the  cornea, 
and  elsewhere.  Termination  by  bulbs  has  been  closely  investi- 
gated by  Krause.  The  bulbs  are  described  as  having  a  diam- 
eter of  ¥V  millimetre,  and  ovoid-shaped  in  man,  with  a  thin 
capsule  of  connective  tissue.  One  or  more  fibres  appear  to 
enter  the  bulb,  and,  penetrating  some  distance,  end  in  a  knob. 
They  have  been  found  in  the  conjunctiva,  in  the  mucous  mem- 
brane of  the  floor  of  the  mouth,  lips,  soft  palate,  and  tongue, 
and  in  the  glans  penis  and  clitoris.  In  the  cavity  of  the  mouth 
they  are  placed  in  the  papillae.  The  bodies  Krause  has  ob- 
served in  the  clitoris  are  somewhat  peculiar  ;  they  are  variously 
shaped,  and  have  a  mulberry-like  surface. 

These  corpuscles,  about  which  there  has  been  so  much  dis- 
cussion, and  which  some  excellent  observers  (Waldeyer,  Arnold) 

1  Frey  :  Das  Mikroskop.,  Leipzig,  1877. 


124  MANUAL    OF   HISTOLOGY. 

had  failed  to  see,  were  investigated  a  few  years  ago  by  Long- 
worth,  of  Cincinnati,  and  their  existence  established  as  a  matter 
of  no  doubt.  He  took  the  human  eye,  freshly  removed  with 
the  conjunctiva,  and  made  the  examination  immediately.  At- 
taching the  conjunctiva  with  threads,  so  that  it  preserved  its 
natural  tension,  he  immersed  it  in  a  -J-  per  cent,  solution  of  os- 
mic  acid,  or  exposed  it  to  the  vapor  of  the  same  solution. 
After  twelve  to  twenty-four  hours  the  membrane  was  deeply 
stained,  and  the  epithelium  could  usually  be  removed  with 
a  brush  or  the  finger-nail.  Next,  a  thin  piece  of  cornea  was 
removed  and  examined  in  water,  or  in  1  to  2  per  cent,  acetic- 
acid  solution.  It  was  then  mounted  in  glycerine.  This  method 
was  preferred  to  the  gold  chloride.  In  some  conjunctive  they 
were  found  almost  entirely  absent ;  in  others,  or  in  certain  por- 
tions, quite  numerous.  The  entire  interior  was  seen  to  be  filled 
with  nucleated  corpuscles.  Waldeyer,  in  commenting  on  the 
work  of  Dr.  Longworth,  agreed  to  it  fully,  and  retracted  his 
former  opinions.  He  places  these  bodies  intermediate  between 
the  tactile  and  Pacinian  bodies. 

The  tactile  corpuscles  of  the  skin  (called  also  Meissner's 
or  Wagner's  corpuscles)  are  to  be  seen  in  the  papillae,  and 
especially  well  in  the  tips  of  the  fingers,  and  in  the  internal 
genitals.  They  have  a  length  of  about  T\  millimetre.  Speci- 
mens hardened  and  preserved  in  the  ordinary  way  show  them 
well.  They  are  oblong,  rounded,  and  marked  by  transverse 
wavy  lines.  A  nerve-fibre  may  be  seen  running  into  their 
centre. 

The  Pacinian  bodies,  discovered  by  Yater,  in  1741,  but  first 
carefully  described  by  Pacini,  of  Pisa,  are  oval  or  pear-shaped 
bodies,  attached  to  the  nerves  like  berries  to  a  stem.  They  are 
found  in  the  subcutaneous  tissues  of  the  finger  (Kolliker),  in 
the  labia  majora,  prostate,  corpora  cavernosa,  and  in  many 
other  places.  They  are  seen  to  the  best  advantage,  however, 
in  the  mesentery  of  the  cat,  where  they  are  so  large  as  to  be 
easily  visible  to  the  naked  eye. 

Cut  out  a  small  piece  of  the  mesentery,  place  it  in  a  weak 
solution  of  osmic  acid  (1 — 100),  and  after  a  few  minutes,  when 
it  has  become  brown,  detach  the  capsule  carefully  with  needles. 
Mounting  at  once  in  glycerine,  the  whole  interior  of  the  Paci- 
nian will  be  superbty  shown,  constituting  one  of  the  most  beau- 
tiful specimens  in  histology.  The  medullated  nerve  may  be 


GENERAL    HISTOLOGY    OF   THE    NERVOUS    SYSTEM.         125 


seen  winding  in  at  one  end  (Fig.  49),  covered  with  a  dense  coat- 
ing of  connective  tissue,  and  accompanied  by  a  small  artery. 
After  penetrating  a  variable  distance,  it  leaves  its  medulla  and 
is  continuous  with  a  straight  fibrillated  band  that  is  called  the 
core.  It  terminates  in  one  or  more  granular  expansions,  appar- 
ently. In  two  cases,  how- 
ever, I  saw  the  nerve  passing 
through  the  body,  giving  off 
its  medulla  on  entering  it,  and 
assuming  it  again  on  leaving. 
This  has  been  observed  by 
Klein,  Pappenheim,  and  oth- 
ers. Round  about  the  core, 
forming  a  series  of  pretty  reg- 
ularly oval  markings,  are  con- 
centric tunics.  Toward  the 
periphery  they  are  at  a  pret- 
ty even  distance  apart.  Be- 
tween them,  applied  closely 
to  the  tunics,1  are  small  ovoid 
nuclei.  The  spaces  between 
the  lamellae  are  probably 
tilled  with  a  clear  fluid.  In 
my  experience  these  bodies 
are  not  successfully  pre- 
served in  glycerine,  even  after 
hardening  in  osmic  acid.  The 
chloride  of  gold  may  answer 
better. 

Nerve  -  terminations  in 
muscle  are  quite  easily  seen. 
It  is  only  necessary  to  take  a 
bit  of  muscle  from  the  thigh 
of  a  frog  just  dead,  and  immerse  it  in  dilute  acetic  acid,  and 
then  in  glycerine.  When  the  tissue  is  thoroughly  transpa- 
rent, as  it  will  be  in  a  few  minutes  (ten  or  fifteen),  there  will 
be  little  difficulty  in  finding  a  medullated  nerve,  and  then  in 
tracing  it  into  a  muscle-fibre.  Reaching  the  sarcolemma,  it 

1  According  to  Schaef  er,  the  nuclei  belong  to  epithelioid  corpuscles  which  cover  the 
tunic  on  both  sides.  Practical  Histology,  p.  134  j  Quarterly  Microscop.  Journ., 
1875. 


FIG.  49. — Pacinian  body  from  the  cat's  mesentery. 


126  MANUAL    OF   HISTOLOGY. 

penetrates  it  at  a  prominence  (Doyere*  s  eminence).  From  tliis 
point  it  divides  into  fibrils,  which  form  delicate  networks,  and 
one,  or  possibly  two  filaments  will  be  seen  to  enter  an  irregular 
body  placed  in  the  centre  of  the  fibre.  This  body  is  highly 
nucleated,  and  may  without  much  difficulty  be  distinguished 
from  the  muscle  nucleus,  which  lies  either  on  the  bundle  or  in 
it.  This  body  is  called  the  motor  ial  plate.  It  is  not  certain, 
however,  that  the  ultimate  fibrils  actually  end  there,  for  in 
some  instances  one  is  in  connection  with  one  side,  and  one  with 
the  other.  Yaricosities  are  described  in  the  primitive  fibrils 
when  osmic  acid  or  chloride  of  gold  is  used. 

Gschleiden,  of  Breslau,  one  of  the  most  recent  writers  on 
this  subject,  has  traced  (in  the  leech)  the  ultimate  fibrils  to  the 
cement  substance  between  the  contractile  muscle-corpuscles 
(unstriped  muscular  tissue).  He  never  saw  them  end  in  plates 
or  in  networks.  Ganglion-cells  are  closely  attached  to  the 
fibres  near  their  termination,  and  they  may  be  unipolar,  bi- 
polar, or  even  multipolar,  the  former  being  the  most  numer- 
ous. 

Termination  of  nerves  in  epithelial  bodies  has  been  de- 
scribed by  a  good  many  observers.  The  demonstration  of  such 
endings,  however,  is  extremely  difficult.  The  ultimate  fibrils 
are  liable  to  be  confounded  with  elastic  tissue,  possibly  with 
connective-tissue  fibres.  To  be  quite  sure  of  their  character 
they  should  be  traced  into  connection  with  nerve- trunks,  on 
the  one  hand,  or  ganglionic  bodies  on  the  other. 

Connective  tissue  of  nerves. — In  our  description  we  have 
adhered  to  the  idea  that  the  sheath  of  Schwann  is  the  one  that 
immediately  incloses  the  medulla,  without  any  intervening 
substance.  Ranvier  has  called  the  first  sheath,  exterior  to 
Schwann' s,  "  the  sheath  of  Henle. "  (Fig.  43,. e.) 
•  The  term  perineurium  is  often  applied  to  the  sheaths  of  the 
funiculus  or  bundle.  The  connective  tissue  separating  the 
funiculi  in  a  large  trunk  has  been  called  the  endoneurium, 
while  epineurium  is  the  great  sheath  'of  the  whole  trunk. 
Each  bundle  or  funiculus,  the  smallest  element  that  we  see  in 
making  a  gross  dissection  of  a  nerve,  is  covered  with  one  or 
more  layers  of  endothelium,  forming  a  special  sheath.  These 
funiculi  do  not  run  parallel  without  anastomosing,  but  two, 
joining,  form  a  third,  which  again  divides. 

There  is  much  practical  difficulty  in  the  way  of  giving  pre- 


BIBLIOGEAPHY.  127 

else  limits  to  these  sheaths,  from  the  fact  that  they  are  apt  to 
be  continuous  with  one  another,  while  one  or  more  may  be 
absent,  according  to  the  size  or  quality  of  the  nerve. 


BIBLIOGRAPHY. 

COHNHEIM.     Virchow's  Archiv.     Vol.  XXXVIII. ,  p.  343.     1867. 

CLEVELAND.  Ueber  d.  feineren  Ban  d.  Markhalt.  Nervenfasern.  Arch.  f.  inikrosk. 
Anat.,  1870.  Vol.  XIII.,  p.  1. 

SCHULTZE,  MAX.     Strieker's  Histology,  p.  117.     1872. 

SCHMIDT.  On  the  Construction  of  the  Dark  or  Double-bordered  Nerve-fibre. 
Month.  Micros.  Journ.,  May  1,  1874. 

LONGWORTH.     Arch.  f.  inikrosk.  Anat.     Vol.  II.     1875. 

SCIIAEFER.     Practical  Histology.     Quart.  Micr.  Journ.,  p.  134.     1875. 

KRAUSE.     Arch.  f.  mikrosk.  Anat.     Vol.  XII.    1876. 

SHAW.  Some  Peculiarities  in  the  Myelinic  Peripheral  Nerves,  etc.  Jour,  of  Nerv. 
and  Ment.  Dis.,  Jan.,  1876. 

GsCHLEiDEN.     Arch.  f.  mikrosk.  Anat.     Vol.  XIV.     1877.  - 

RANVIER.     Logons  sur  1'histoire  du  systeme  nerveux.     1878. 

KEY  and  RETZIUS.     Stud,  in  d.  Anat.  d.  Nerv. -Syst.  V.  &  H.'s  Jahresb.     1878. 

His,  W.     Arch.  f.  Anat.  u.  Phys.,  p.  455.    1879. 

RAWITZ,  B.     Arch.  f.  Anat.  u.  Phys.     1879. 

RUMPF.  Zur  Histol.  d.  Nervenf aser,  etc.  tint.  d.  Phys.  Inst.  d.  Univ.  Heidelberg. 
Vol.  II. 

SCHULTZE,  H.     Axencylinder  u.  Ganglienzelle.     Arch.  f.  Anat.  u.  Phys.     1879. 

KUHNE,  W.  Zur  Histol.  d.  motor.  Nervenendig.  Tint.  d.  phys.  Inst.  d.  Univ.  Heidel- 
berg. Vol.  IT. 

HESSE,  FR.  Zur  Kennt.  d.  peripher.  Markhalt.  Nervenf  aser.  Arch.  f.  Anat.  u. 
Phys.  1879. 

KUHNE,  W.,  and  STEINER,  J.  Beobacht.  ueber  Markhaltige  u.  Marklose  Nerven- 
fasern. Unt.  d.  Phys.  Inst.  d.  Univ.  Heidelberg.  Vol.  III. 

His,  W.  Ueber  d.  Anfange  d.  peripher.  Nerven-System.  Arch.  f.  Anat.  u.  Phys., 
p.  455.  1879. 

WALDEYER.  Ueber  die  Endig.  d.  sensiblen  Nerven.  Arch.  f.  mikros.  Anat.  Vol. 
XVII.,  pp.  367-382.  1880. 

RANVIER.     Le9ons  d'anat.  gen.    App.  nerveux  term. ,  etc.     Paris,  1880. 


PART    II. 


CHAPTER  X. 

MUSCULAR   FIBRE. 

BY  THOMAS  DWIGHT,  M.D., 

Instructor  in  Topographical  Anatomy  and  in  Histology  at  Harvard  University. 

THE  physiological  attribute  of  muscular  tissue  is  contrac- 
tility. This  may  or  may  not  be  under  the  control  of  the  will. 
The  structure  of  voluntary  muscular  fibre  is  very  different  from 
that  of  the  involuntary. 

This  distinction,  however,  is  not  absolute.  The  muscular 
fibre  of  the  heart  presents  a  structure  intermediate  between  the 
two  typical  forms.  Striped  fibres  are  found  in  some  places,  as, 
for  instance,  in  the  upper  part  of  the  oesophagus,  over  which 
most  people  have  little  or  no  control.  There  is  also  an  un- 
doubted difference  in  the  manner  of  contraction  among  volun- 
tary muscles.  Whether  this  is  associated  with  a  difference  of 
structure  is  an  interesting  but  very  uncertain  question  that 
will  be  alluded  to  later. 


INVOLUNTARY  MUSCULAR  FIBRE. 

Unstriped  muscular  fibre  is  shown  with  great  advantage  in 
the  bladder  of  the  frog.  It  should  be  stained  with  gold  chlo- 
ride, logwood,  or  carmine.1  After  the  specimen  has  lain  two 

1  If  one's  object  is  to  study  the  muscular  tissue  only,  gold  has  no  advantages  over 
the  other  agents,  and  should  not  be  used,  because  it  is  less  certain.  The  writer  has 
obtained  remarkably  beautiful  stainings  of  the  bladder  by  using  carmine,  following 
Beale'o  method. 


INVOLUNTARY   MUSCULAR   FIBRE. 


129 


or  three  days  in  glycerine,  the  lining  epithelium  is  easily 
brushed  off.  The  bladder  of  the  frog  is  peculiarly  favorable, 
because  it  affords  an  opportunity  of  studying  the  fibres,  both 


Fio.  50. 


Fia.  51. 


Fio.  62. 

Fio.  50.— Muscular  fibres  treated  with  serum.  FIG.  51.— Muscular  fibres  from  the  muscular  tissue 
of  the  intestine,  isolated  by  means  of  nitric  acid.  FIG.  52. — Muscular  fibres  from  a  pleuritic  membrane. 
J.  Arnold. 

separately  and  in  bundles,  in  its  walls  and  in  the  coats  of  the 
minute  arterioles  which  nourish  it. 

The  plain  fibre  is  composed  simply  of  one  or  more  elongated 


130  MANUAL   OF   HISTOLOGY. 

cells.  (Fig.  50.)  The  nucleus  is  at  about  the  middle.  The  cell 
swells  out  around  the  nucleus,  and  quickly  contracts  again  be- 
yond it.  A  small  cell,  such  as  is  found  in  the  wall  of  a  small 
blood-vessel,  is  consequently  spindle-shaped,  but  we  find  many 
in  the  frog's  bladder  that  run  out  into  fine  threads  of  indefinite 
length.  Sometimes  one  end  of  a  cell  divides  into  two  fibres. 
(See  Figs.  51  and  52.) 

The  nucleus  sometimes  appears  to  be  homogeneous,  though 
it  usually  contains  one  or  more  granules,  sometimes  considered 
to  be  nucleoli.  When  using  a  high  power  the  writer  has  some- 
times found  that  the  nucleus  contained  many  granules,  so  ar- 
ranged as  to  suggest  very  strongly  a  transverse  stria tion.  A 
row  of  granules  at  each  end  of  the  nucleus  is  sometimes  found. 
Muscular  fibres  in  the  walls  of  small,  transparent  blood-vessels 
are  very  instructive  objects,  because  by  changing  the  focus  we 
can  observe  them  as  they  curve  round  the  vessel,  both  in  longi- 
tudinal and  in  transverse  section.  At  those  places  where  a 
transverse  section  of  one  end  of  the  cell  is  in  focus  we  see  what 
appears  to  be  a  granule  merely.  If  another  part  near  the  nu- 
cleus is  brought  into  focus,  it  shows  as  a  small  circle,  while  if 
the  nucleus  happens  to  be  cut  transversely,  it  gives  the  effect 
of  a  dark  spot  inside  a  circle. 


VOLUNTARY  MUSCULAR  FIBRE. 

No  tissue  is  more  easily  recognized  than  striped  muscular 
fibre,  yet  none  is  more  difficult  to  understand.1 

The  fibres  are  cylinders  or  irregular  prisms  of  varying  length. 
'Their  diameter  in  the  human  body  varies,  according  to  Frey, 
from  .0113  to  .0563  mm.  Each  fibre  is  tightly  inclosed  in  a  struc- 
tureless elastic  membrane,  called  the  sarcolemma.  This  sheath 
is  not  very  easily  demonstrated  ;  but  if  fresh  muscle  be  roughly 
picked  to  pieces  in  water,  shreds  of  it  may  be  seen  at  the  torn 
ends  of  fibres,  and  sometimes  it  can  be  made  out  where  the 
muscular  substance  has  been  injured  in  the  course  of  a  fibre. 

1  Any  attempt  at  an  account  of  the  many  views  that  have  been  and  are  held, 
Would  make  this  article  far  too  long.  A  few  only  will  be  mentioned,  and  these  inci- 
dentally. It  is  hoped  that  this  defect,  if  it  be  one,  will  be  compensated  for  by  the 
lulness  of  the  bibliography. 


VOLUNTARY   MUSCULAR   FIBRE.  131 

The  existence  of  a  sarcolemma  being  admitted,  it  is  clear 
that  it  must  be  highly  elastic  so  as  to  accommodate  itself 
to  the  changes  both  of  length  and  breadth  which  the  fibre 
undergoes.  The  phenomena  of  contraction  show,  moreover, 
that  it  must  be  attached  at  definite  points  to  the  muscular 
substance. 

Fresh  muscular  fibre  of  a  vertebrate  animal,  when  teased 
out  and  examined  under  a  moderately  high  power,  presents  a 
series  of  alternate  black  and  white  cross  stripes,  which  are 
held  to  be  characteristic  of  voluntary  muscle.  (Fig.  53.)  This 
appearance  is  beautifully  distinct  in  some 
fibres,  and  very  vague  in  others.  It  may 
vary  greatly  in  different  parts  of  the  same 
fibre  ;  the  stripes  may  run  perfectly  straight 
across  the  fibre  ;  they  may  present  a  uni- 
form curve,  or  they  may  be  interrupted  at 
intervals,  some  parts  of  the  line  being  in 
advance  of  others.  (See  Fig.  53.) 

As  a  fibre  taken  from  an  animal  im- 
mediately after  death  naturally  draws  it- 
self together  (without,  however,  necessarily 

J  FIG.  53.—  Striped  muscular 

presenting  the  phenomena  of  physiologi-    *»>«>:  «>  black  8trfpe;  &.  fc- 

r  *-.-'*  *'*  termediate  stripe;     c,    white 

cal  contraction),  it  is  desirable  to  ascertain  *«  nucleus- 


whether  this  modifies  the  appearances.  To 

do  this,  fibres  from  a  recently  killed  animal  should  be  ex- 

amined in  a  state  of  extension.    A  cut  should  be  made  in  the 

body  of  a  muscle,  a  few  fibres  teased  out  and  stretched  on  the 

slide  under  the  covering  glass  before  their  attached  ends  are 

divided. 

It  will  be  seen  that  the  light  stripe  is  more  affected  by  the 
stretching  than  the  dark  one,  though  both  are  broader  than  in 
the  non-extended  fibre  ;  but  the  most  important  effect  is  the 
appearance,  often  seen  with  high  powers,  of  a  very  narrow,  in- 
terrupted black  line  in  the  middle  of  the  light  band. 

Beside  this  cross  striation,  the  fibres  of  vertebrates  show 
more  or  less  plainly  minute  longitudinal  lines.  It  is  to  be  no- 
ticed that  when  the  cross  stripes  are  very  distinct  the  longitu- 
dinal ones  are  very  faint,  or  even  invisible,  and  that  when  the 
latter  are  well  marked  the  former  are  the  reverse  of  it.  Some 
reagents  tend  to  divide  a  fibre  into  disks,  others  into  fibrillae. 
Among  the  former  are  solutions  of  acetic  acid  in  water  (1  in 


132  MANUAL    OF    HISTOLOGY. 

100—200),  hydrochloric  acid  (1  in  50—200),  and  among  the  latter 
a  solution  of  chromic  acid  (1  in  200).  It  is  very  probable  that 
the  amount  of  longitudinal  striation  varies  in  different  muscles, 
being  related,  perhaps,  to  physiological  properties,  or  possibly 
the  result  of  mechanical  causes.  It  is  certain  that  both  kinds 
of  striation  may  be  found  in  great  perfection  in  fibres  treated 
with  almost  any  reagent  that  does  not  destroy  them.  Some- 
times muscle  is  seen  to  be  split  into  fibrillse,  each  of  which 
shows  the  transverse  stripe,  though  the  shreds  are  so  fine  that 
each  disk  is  represented  by  a  dot  merely.1  This  may  be  de- 
tected very  well  in  the  muscle  of  the  lobster  after  it  has  been 
picked  to  pieces  in  glycerine. 

Returning  to  the  transverse  stripes  in  vertebrates,  the  striae 
are  very  near  together  in  the  frog,  and  thus  this  useful  animal 
is  not  specially  desirable.  The  muscle  of  the  rabbit  is  much 
better,  and  human  muscle  is,  perhaps,  better  still.  The  muscle 
of  the  human  embryo  in  the  last  months  of  pregnancy  is  par- 
ticularly good.  A  very  high  power  will  often  show  the  narrow 
black  line  in  the  midst  of  the  white  band.  Sometimes  one  edge 
of  each  black  stripe  will  be  very  sharply  marked  against  the 
glaring  white,  while  the  other  side  will  present  a  less  marked 
contrast.  If  the  stage  of  the  microscope  admits  of  rotation,'  in- 
structive effects  can  also  be  obtained.  As  the  field  turns  round, 
the  brightness  at  the  sharp  border  of  the  black  stripe  gradually 
decreases,  to  return  on  the  other  side.  Again,  this  change  may 
not  occur.  Sometimes,  when  the  upper  edge  of  the  fibre  is  pre- 
cisely in  focus,  the  black  and  white  stripes  may  be  made  to  ap- 
parently exchange  places,  if  the  lens  is  slightly  depressed.  This 
is  probably  to  be  accounted  for  as  follows :  First,  we  may  for 
the  present  assume  that  the  black  and  white  bands  are  caused 
by  disks  of  different  nature.  Take  a  series  ,of  such  disks  and 
imagine  them  somewhat  inclined  to  one  side,  like  a  roll  of 
coins  on  their  edges  leaning  against  a  support.  A  vertical  line, 
representing  the  line  of  vision,  that  passes  through  a  black  disk 
at  the  upper  border  of  the  roll  will  strike  a  light  one  at  a 
deeper  level.  A  peculiar  effect  may  be  obtained  by  removing 
the  diaphragm  and  employing  very  oblique  light.  The  black 


1  The  fact  that  muscle  removed  from  the  body  can  be  reduced  to  fibrillae  does  not 
prove  that  these  are  pre-existing  elements. 

2  It  is  to  be  regretted  that  this  movement  is  not  more  common. 


VOLUNTARY    MUSCULAR    FIBRE. 


133 


band  then  is  often  replaced  by  two  narrow  black  lines  with  a 
light  space  between  them.  This  is  more  frequently  observed 
when  the  rays  strike  the  fibre  longitudinally. 

The  fibres  of  invertebrates,  though  on  the  same  plan  as 
those  of  higher  animals,  are  better  fitted  for  study,  because  the 
elements  are  farther  apart,  and  because  the  phenomena  of  con- 
traction may,  in  some  cases,  at  least,  be  observed  under  the 
microscope. 

The  muscles  from  the  thorax  and  legs  of  large  flies  are  very 
good.  Merkel  recommends  that  they  be  examined  in  fresh  al- 
bumen from  the  egg,  in  which  they  will  continue  to  contract. 
The  fibre  is  crossed  by  narrow  black  stripes  which,  be  it  re- 
membered once  for  all,  correspond  to  the  black  stripes  of  ver- 
tebrate muscle.  On  each  side  of  these  stripes  there  is  a  bright, 
glittering  border,  which  gradually  shades  off  into  a  dull  band, 
midway  between  the  two  stripes.  The  substance  between  the 
black  stripes  is  all  of  one  nature,  the  difference  between  its 
middle  and  end  portions  being  an 
optical  effect.  The  dull  band  corre- 
sponds to  the  fine  line  which  high 
powers  reveal  in  vertebrate  muscle. 
Its  greater  breadth  is  due  to  the 
greater  distance  of  the  black  stripes. 

Fibres  from  the  legs  and  wings 
of  the  large  water-beetles  (Hydro- 
philus  and  Dytiscus)  are  admirable 
objects.  Schafers  valuable  obser- 
vations were  made  on  those  of  the 
legs.  He  found  the  black  stripe  to 
consist  of  a  double  row  of  highly 
refracting  granules,  which  were  the 
ends  of  dumb-bells  embedded  in  the 
contractile  substance.  These  struc- 
tures are  arranged  side  by  side,  the 

adjacent  ends  of  the  dumb-bells  forming  the  stripe,  while  the 
handles  constitute  the  slight  longitudinal  striations.  (See  Fig. 
54.)  The  bright  borders  are  due  to  the  refraction  of  light  from 
the  spherical  heads  of  the  dumb-bells.  It  is  clear  that  they 
must  cause  a  greater  amount  of  rays  to  pass  through  the  sub- 
stance directly  beside  them  than  go  through  the  substance 
midway  between  them,  which  latter  appears  dark  in  conse- 


FIG.  54. — Muscle  of  large  water-beetle 
(Dytiscus) :  a,  dull  hand ;  6,  bright  space 
around ;  c,  the  highly  refractive  ends  of 
the  dumb-bells ;  d,  the  handles  of  the  dumb- 
bells ;  6,  sarcolemma.  After  Schafer. 


134  MANUAL    OF    HISTOLOGY. 

quence.  Some  years  before  Schafer's  theory  was  advanced 
Heppner  had  shown  that  the  bright  borders  of  the  black  stripe 
must  be  due  to  the  reflection  of  rays  through  them  from  the 
surface  of  the  stripe.  The  phenomena  observed  on  rotating 
the  stage  of  the  microscope  are  in  accordance  with  this  theory. 
There  are,  no  doubt,  some  apparent  exceptions,  but  these  lose 
their  weight  when  we  consider  how  many  .elements  there  are 
that  complicate  the  problem.  If,  for  instance,  as  is  often  the 
case,  the  disks  do  not  present  their  edges  quite  evenly  to 
the  eye  of  the  observer,  but  are  somewhat  inclined,  like  the 
roll  of  coins  above  mentioned,  the  conditions  are  at  once 
changed.  Again,  light  thrown  up  vertically  through  a  small 
diaphragm  must  produce  different  effects  on  the  object  from 
light  striking  it  very  obliquely. 

Some  years  ago  the  writer  was  fortunate  enough  to  discover 
an  excellent  object  for  the  study  of  living  muscular  fibre  in  the 
detached  legs  of  the  Gyrinus.  This  is  a  small  beetle,  known 
in  the  country  as  the  "  lucky  bug,"  which  describes  most  ec- 
centric figures  on  the  surface  of  ponds.  A  leg  should  be  cut 
off  close  to  the  body,  and  examined  in  a  drop  of  water  under  a 
very  thin  covering  glass.  The  shell  is  transparent,  and  as  the 
muscles  are  undisturbed,  except  in  the  segment  cut  in  remov- 
ing the  leg,  they  are  in  a  perfectly  normal  condition,  lacking 
only  their  vascular  and  nervous  supply.  They  will  frequently 
contract  for  more  than  an  hour,  if  the  covering  glass  be  lightly 
tapped  occasionally.  The  part  of  the  leg  known  as  the  tibia, 
which  is  easily  recognized  by  a  large  Y-shaped  air-tube,  has 
the  thinnest  shell,  and  is  usually  the  best  place  for  study, 
though  occasionally  better  views  are  obtained  in  the  two  parts 
next  above  it,  in  which  it  is  easier  to  find  a  single  layer  of  fibres. 
The  leg  is  very  apt  to  flex  itself  between  the  femur  and  tibia, 
thus  obscuring  one  of  the  best  places.  If  necessary,  this  can 
be  prevented  by  putting  a  thin  piece  of  paper  against  the  inner 
side  of  the  leg.  The  anterior  pair  of  legs,  which  project  for- 
ward, are  made  on  another  plan,  and  are  less  desirable.  A 
very  high  power  is  necessary,  as,  for  instance,  Hartnack's  10 
immersion  lens.  Much  practice  also  is  needed  to  follow  the 
steps  of  contraction,  and  indeed  this  can  be  done  only  when  it 
has  become  very  slow. 

The  fibre,  when  at  rest  and  moderately  stretched,  appears 
to  be  a  cylinder  with  straight  edges,  and  composed  of  a  semi- 


VOLUNTARY   MUSCULAR    FIBRE. 


135 


fluid,  transparent  ground-substance.  This  is  crossed  by  the 
black  stripes  with  shining  borders,  such  as  have  been  described. 
The  black  stripe  usually  appears 
granular,  and  may  be  divided  into 
two  parallel  rows  of  granules.  Some- 
times the  two  borders  are  equally 
bright ;  sometimes  one  much  out- 
shines the  other.  Some  fibres  are 
found  which,  not  being  subjected 
to  any  tension,  are  much  more 
drawn  together.  The  black  bands 
are,  perhaps,  only  half  so  far  apart 
as  in  the  case  just  described.  They 
are  never  divided  into  two,  and 
though  some  appear  granular, 
others  are  homogeneous.  The  edges 
of  the  fibre  are  no  longer  straight, 
but  slightly  scalloped,  the  centre 
of  each  projection  being  midway 
between  the  black  stripes.  (See 
Fig.  55.) 

When  active  contraction  takes 
place,  the  whole  fibre  is  involved, 
and  presents  nothing  but  a  series 
of  transverse  black  and  white  bands 
with  scalloped  edges.  To  study  the 
successive  stages  of  contraction  we 
must  wait  until  it  is  feeble  and  in- 
volves but  a  small  part  of  the  fibre. 
It  runs  like  a  wave  from  one  end  of 
the  fibre  to  the  other,  pauses  a  mo- 
ment, and  then  runs  back  again, 
and  sometimes  starts  anew,  but  with 
diminished  force.  It  is  hard  to  fol- 
low the  steps,  for  the  elements  are 
changing  their  shape  and  position 
at  the  same  time  ;  the  black  stripes 
become  broader,  less  granular,  and 
each  runs  toward  its  neighbor  in 
the  direction  of  the  wave  ;  the  gray  band  disappears,  and  the 
edge  of  the  fibre  bulges.  As  the  elements  in  front  of  the 


FiQ.  55.  —  Semi-diagrammatic  repre- 
sentations of  muscular  fibres  of  Gyrinus. 
Fibre  supposed  to  be  in  situ  and  showing 
the  different  appearances  which  the  black 
stripe  may  present.  The  wave  of  contrac- 
tion is  travelling  toward  A.  At  C  we 
notice  that  a  part  of  the  fibre,  after  con- 
traction, has  been  subjected  to  stretching 
after  the  passage  of  the  wave;  at  B  the 
elements  are  in  a  state  of  active  contrac- 
tion. The  longitudinal  striation  made 
unavoidable  in  the  woodcut,  does  not,  as  a 
rule,  exist  in  the  living  fibre. 


136  MANUAL    OF   HISTOLOGY. 

wave  enter  into  the  contracted  condition,  those  behind  as- 
sume their  normal  state  at  first,  but  do  not  retain  it,  for  they 
are  immediately  subject  to  a  severe  stretching  by  the  course 
of  the  wave,  and  present  new  and  very  instructive  appear- 
ances. The  fibre  becomes  much  narrower,  the  black  stripes 
are  resolved  into  two  rows  of  granules  some 
distance  apart.  The  whole  substance  of  the 
fibre  is  lighter  than  in  the  other  conditions, 
and  though  the  bright  borders  of  the  stripes 
are  still  there,  they  are  much  less  glaring,  and 
present  less  contrast  with  the  intermediate  por- 
tion. 

In  some  of  these  fibres  an  indistinct  longi- 
tudinal striation  is  seen,  but  the  writer  is  not 
satisfied  that  it  is  in  the  substance  of  the  fibre. 

Transverse  sections  of  muscle  have  been  ap- 
pealed  to  for  elucidation  of  the  structure  of  the 
Frgey.°bnheim1sareas'  fibl>e-  Cohnheim  showed  a  network  of  whitish 
lines  surrounding  small,  dull-colored  polygons 
on  cross-cuts  of  frozen  muscle  (Pig.  56).  The  muscles  of  the 
crab  are  said  to  show  this  particularly  well.  Schafer  found 
in  the  muscles  of  the  water-beetle  the  appearance  of  granules 
on  a  clear  ground.  A  similar  appearance  is  seen  in  the  fibres 
of  vertebrates.  The  writer  has  observed  in  the  cross-section  of 
fibres  from  the  tongue  of  the  mocassin  snake,  granules  which 
presented,  at  least,  the  suggestion  of  bright  points  in  their  cen- 
tre. In  some  fibres  these  were  collected  into  groups,  separated 
by  clear  spaces. 

Cohnheim's  areas  cannot  be  considered  equivalent  to  fibril- 
ISD,  but  rather,  as  Kolliker  claims,  to  bundles  of  them,  sup- 
posing always,  we  would  add,  that  fibrilke  exist  at  all.  It  is 
pointed  out  in  the  account  of  the  transverse  striae  that  these 
are  often  interrupted,  and  there  is  no  doubt  that  this  may  be 
due  to  the  limits  of  the  muscle-columns.  Of  course,  we  must 
assume  that  there  are  many  more  columns  than  would  be  in- 
ferred from  these  interruptions  ;  for  if  the  transverse  stripes  of 
two  neighboring  columns  exactly  correspond,  no  break  will 
appear. 

,  Nuclei  and  muscle-corpuscles. — In  mammalian  m  uscle  acetic 
acid  demonstrates  a  number  of  oval  nuclei  which  may  contain 
one  or  more  nucleoli.  Their  long  axis  runs  in  the  same  direc- 


VOLUNTARY   MUSCULAR   FIBRE.  137 

tion  as  that  of  the  fibre.  A  small  amount  of  granular  matter 
may  be  seen  at  their  extremities.  Cross  cuts  of  fibres  show 
that,  with  possibly  some  exceptions,  they  lie  directly  beneath 
the  sarcolemma.  In  the  frog,  and  in  many  invertebrates,  as  the 
beetles,  they  lie  in  the  substance  of  the  fibre,  and,  especially 
in  the  latter  class  of  animals,  are  surrounded  by  a  mass  of 
granular  protoplasm.  Weber  denies  that  in  the  adult  frog 
they  are  surrounded  by  this  mass. 

Conclusions. — From  what  precedes,  it  seems  demonstrated 
that  striped  muscular  fibre  consists  of  a  transparent,  semifluid 
ground-substance,  which  is  the  contractile  element.  At  certain 
intervals  a  double  layer  of  minute  granules  or  spherules  is 
placed,  which  practically  forms  a  transverse  disk.  The  refrac- 
tion of  the  light  causes  the  substance  bordering  this  disk  to 
appear  brighter  than  the  intermediate  portion,  which  is  only 
occasionally  seen  in  mammalian  muscle  as  an  indistinct  and 
usually  a  broken  line,  because  the  black  stripes  are  so  near  to- 
gether that  the  bright  borders  of  two  neighboring  ones  coalesce. 
In  invertebrates,  as  beetles,  for  instance,  they  are  so  far  apart 
that  the  dim  stripe  is  proportionally  broad,  but  it  necessarily 
disappears  when  by  contraction  the  black  stripes  are  brought 
nearer  together.  Variations  in  the  direction  of  the  light,  or 
any  obliquity  of  the  disks,  will  cause  peculiar  effects,  well- 
nigh  defying  analysis.  The  writer' s  views  coincide,  in  the  main, 
with  Schafer's,  except  that  he  cannot  accept  the  "handles  "  of 
the  latter's  dumb-bell-shaped  structures.  As  the  writer  has 
stated  in  another  paper,  muscles  in  the  leg  of  the  Gyrinus 
which  have  been  exhausted  by  electricity  show  the  stripes  very 
indistinctly,  and  contain  a  number  of  stray  granules.  Klein 
has  pointed  out  that  if  fresh  muscular  fibre  of  the  frog  is 
teased  out  in  salt  solution,  when  a  break  of  the  substance  ocr 
curs  inside  the  sarcolemma,  "  inside  this  tube  a  greater  or  less 
number  of  granules  are  observed  in  active  molecular  move- 
ment." These  observations  appear  to  confirm  the  views  given 
above. 

A  good  deal  has  been  written  about  the  effect  of  polarized 
light  on  muscular  fibre,  and  very  different  results  have  been 
reached.  Ranvier  thinks  it  of  no  value  in  the  discussion,  be- 
*  cause  the  same  substance  may  be  either  doubly  or  singly  re- 
fracting, according  to  the  pressure  to  which  it  is  subjected. 
This  is  certainly  a  strong  argument  against  its  value,  espe- 


138  MANUAL    OF   HISTOLOGY. 

cially  in  view  of  the  discrepancy  of  the  observations  made 
with  it. 

Each  fibre  is,  moreover,  divided  longitudinally  into  a  vary- 
ing number  of  what  are  called  muscle-columns,  held  together 
probably  by  a  delicate  cement.  Between  these  are  lodged  the 
muscle-corpuscles  in  the  lower  forms  of  animals.  In  opposition 
to  most  authorities,  the  writer  is  inclined  to  question  the  exist- 
ence of  fibrillse  in  the  living  muscle,  at  all  events,  as  essential 
parts  of  its  structure.  The  granular  appearance  of  cross  sec- 
tions is  in  accord  with  the  views  given  above,  and  does  not 
necessarily  imply  the  presence  of  fibrillse. 

Peculiarities  of  voluntary  muscles  of  different  functions. 
— Ranvier  was  the  first  to  discover  a  physiological  and  struc- 
tural difference  in  the  red  and  white  muscles  of  the  rabbit' s 
leg  and  in  some  other  animals  where  both  kinds  exi^t.  He 
found  that  the  semitendinosus  of  the  rabbit,  a  red  muscle,  if 
acted  on  by  an  induction  current,  gradually  contracted  till  it 
became  tetanized,  and  remained  so  until  the  current  was 
stopped,  when  it  gradually  relaxed.  White  muscles,  on  the 
other  hand,  when  treated  in  the  same  way,  contracted  sud- 
denly, and  continued  to  give  jerks  corresponding  to  the  inter- 
ruptions of  the  current  as  long  as  it  was  continued.  With  its 
cessation  the  muscle  instantly  returned  to  its  original  length. 
From  this  he  concludes  that  the  white  muscles  are  those  of 
sudden  action,  while  the  red  ones  serve  to  regulate  power  and 
to  maintain  equilibrium.  As  to  structure,  he  found  out  that 
the  white  muscles  had  a  very  distinct  transverse  striation,  and 
a  very  faint  longitudinal  one,  while  in  the  red  the  longitudinal 
lines  were  very  marked,  interrupting  the  cross  ones  at  many 
points,  and  giving  the  fibre  a  granular  appearance.  The  nu- 
clei were  much  more  numerous  in  the  red.  fibres,  and,  instead 
of  being  flattened  and  situated  just  beneath  the  sarcolemma,  as 
in  the  white,  were  oval  and  projected  into  the  fibre,  some  even 
lying  in  its  interior. 

Eanvier  showed  later  that  the  vascular  supply  of  the  red 
muscles  differed  from  the  usual  arrangement,  which  consists 
simply  in  elongated  meshes  of  capillaries  in  the  main  parallel 
with  the  fibres.  In  red  muscle,  not  only  were  the  minute  ves- 
sels more  numerous,  but  the  longitudinal  capillaries  were  more 
varicose,  the  meshes  nearly  as  broad  as  long,  and  the  transverse 
vessels,  both  of  the  capillaries  and  small  veins,  presented  fusi- 


VOLUNTARY   MUSCULAR   FIBRE. 


139 


form  dilatations,  the  object  being,  as  he  points  out,  to  keep  the 
muscle  supplied  with  oxygen  during  its  long-continued  con- 
traction, which  must  interrupt  the  circulation. 

E.  Meyer  has  since  shown  that  Kanvier  was  over-hasty  in 
his  generalization.  What  is  true  of  the  semitendinosus  of  the 
rabbit  is  not  necessarily  true  of  other  red  muscles. 

The  writer  is  able  to  confirm  this  statement.  As  to  the  dif- 
ference between  the  semitendinosus  and  white  muscle,  he  is  in- 
clined to  admit  the  greater  number  of  nuclei  of  the  former,  but 
the  difference  in  the  stripes  did  not  seem  to  him  conclusive. 
The  peculiarity,  however,  of  the  minute  blood-vessels  of  the 
semitendinosus  is  very  striking  ;  but  in  another  red  muscle  of 
the  rabbit' s  thigh  he  did  not  find  the  same  arrangement.  The 
richness  of  the  capillary  network  varies  greatly  in  different 
muscles  of  the  same  animal.  Future  investigations  will,  per- 
haps, show  that  modifications  in  the  arrangement  of  the  minute 
blood-vessels  correspond  with  the 
function  of  the  muscle. 

The  termination  of  muscle  in  ten- 
don.— This  occurs  in  several  ways. 
Sometimes  the  fibre  divides  again  and 
again,  ending  in  small  bundles  of 
fibrillse  which  have  lost  all  muscular 
characteristics.  Again,  instead  of 
spreading  out,  a  fibre  may  become 
pointed,  and  the  enveloping  sarco- 
lemma,  reinforced  with  more  or  less 
fibrous  tissue,  runs  on  as  a  delicate 
tendon.  Both  these  modes  of  end- 
ing can  be  seen  in  the  tongue.1  The 
cases  in  which  a  fibre  loses  its  stria- 
tion,  and  is  apparently  continued  as 
a  tendon  of  about  the  same  size, 
present  greater  difficulties.  By  sep- 
arating the  fibres  of  a  frog  killed 
by  immersion  in  hot  water,  Ranvier  has  succeeded  in  demon- 
strating that  the  sarcolemma  incloses  the  tendinous  end  of  the 
fibre.  The  whole  subject,  however,  of  the  ending  of  the  fibres 
is  not  exhausted. 

1  Thin  sections  of  the  hardened  tongue  of  a  small  animal  are  to  be  recommended, 
not  only  for  the  study  of  this  point,  but  for  that  of  striped  muscle  in  general. 


FIG.  57.  —  Anastomosing  muscular 
fibre  of  the  heart,  seen  in  a  longitudinal 
section.  On  the  right,  the  limits  of  the 
separate  cells  with  their  nuclei  are  ex- 
hibited somewhat  diagrammatically. 
After  Schweigger-Seidel.  J.  Arnold. 


140  MANUAL    OF   HISTOLOGY. 

The  muscular  fibre  of  the  heart. — This  is  transitional  in 
structure  between  the  voluntary  and  the  involuntary.  The 
fibres  of  the  heart  of  the  frog  resemble  chiefly  the  latter,  being 
made  of  elongated,  narrow,  nucleated  cells,  which  differ  from 
it  only  in  being  transversely  striped.  In  the  mammalia  the 
fibres  are  broader  and  composed  of  nucleated  cells  placed  end 
to  end.  These  cells  frequently  give  off  lateral  processes  which 
support  others,  thus  forming  a  network  of  fibres.  The  cells 
have  both  a  longitudinal  and  a  transverse  series  of  stripes, 
but  the  latter  are  not  so  clear  as  in  well-marked  voluntary 
muscle. 


BIBLIOGRAPHY. 

BOWMAN.     On  the  Structure  and  Movements  of  Voluntary  Muscle.      Philosoph. 

Transactions.     1840-41. 

AMICI.     Ueber  die  Muskelfaser.     Virchow's  Archiv.    Bd.  XVI.     1859. 
WEISMANN.     Ueber  die  Muskulatur  des  Herzens  beim  Menschen  und  in  der  Thier- 

reihe.     Reichert  &  Du  Bois-Reymond's  Archiv.     1861. 
IBID.     Ueber  die  Verbindung  der  Muskelfasern  mit  ihren  Ansatzpunkten.     Zeit- 

schrift  fiir  ration.  Medicin.    3te  Reihe.     Bd.  XII.     1861. 
COHNHEIM.     Ueber  den  feineren  Bau  der  quergestreiften  Muskelfaser.     Virchow's 

Archiv.     Bd.  XXXIV.     1865. 

DWIGHT.     The  Structure  and  Action  of  Striated  Muscular  Fibre.     Proceedings  Bos- 
ton Soc.  Nat.  Hist.    Vol.  XVI.     1873. 
SCHAEFEB.     On  the  Minute  Structure  of   the  Leg  Muscles  of  the  Water-Beetle. 

Philos.  Transact.     1873. 
ENGELMANN.    Mikroskopische  Untersuchungen  iiber  die  quergestreifte  Muskelsub- 

stanz.     Pfluger's  Archiv.     Bd.  VII.     1873. 
KSLLIKEB.     Handbuch  der  Gewebelehre.     Leipzig,  1867. 
HENSEN.    Arbeiten  aus  dem  Kieler  physiologischen  Institut.     1868. 
HEPPNEB.     Ueber  ein  Eigenthumliches  Verhalten  der  quergestreiften  Muskelfaser. 

Archiv  fiir  mikroscop.  Anat.     Bd.  V.     1869. 
DOENITZ.     Beibrage  ziir  Kenntniss  der  quergestreiften  Muskelfaser.    Reichert  &  Du 

Bois-Reymond's  Archiv.     1871. 

SCHWEIGEB-SEIDEL.     The  Heart.     Strieker's  Histology.     1872. 
MEBKEL.    Der  quergestreifte  Muskel.      Archiv  fiir  mikro.  Anatomic.    Bd.  VIII. 

1872. 
BRUECKE,  E.    The  Behavior  of  Muscular  Fibres  when  examined  by  Polarized  Light. 

Strieker's  Histology.     1872. 
SACHS.     Die  quergestreifte  Muskelfaser.      Reichert  &  Du  Bois-Reymond's  Archiv. 

1872. 
WAGENEB.    Ueber  die  quergestreifte  Muskelfibrille.     Archiv  fiir  mikro.  Anat.   Bd. 

IX.     1873. 


BIBLIOGRAPHY.  141 

IBID.     TJeber  einige  Erscheinungen  an  den  Muskeln  lebendiger  Corethra  plumicornis- 

larven.     Archiv.  ftir  mikro.  Anat.     Bd.  X.  1874. 
KAUFMANN.     Ueber  Contraction  der  Muskelfaser.     Reichert  &  Du  Bois-Reymond's 

Archiv.     1874. 

THIN.     On  the  Minute  Anatomy  of  Muscle  and  Tendon.     Edinburgh  Medical  Jour- 
nal.    Sept.,  1874. 
WEBER.     Note  sur  les  noyaux  des  muscles  stries  chez  la  grenouille  adulte.    Archives 

de  physiologic.     1874. 
RANVIER.     De  quelques  fait  relatifs  a  1'histologie  et  a  la  physiologic  des  muscles 

stries.     Archives  de  phys.     1874. 
IBID.     Note  sur  les  vaisseaux   sanguins  et  la  circulation  dans  les  muscles  rouges. 

Archives  de  phys.     1874. 

IBID.     Traite  technique  d'histologie.     Paris,  1875. 

FREDERICQ.     Generation  et  structure  du  tissu  musculaire.     Bruxelles,  1875. 
MEYER.     Ueber  rothe  und  blase  quergestreifte  Muskeln.      Reichert  &  Du  Bois- 

Reymond's  Archiv.     1875. 
FREDERICQ.     Note  sur  la  contraction  des  muscles  stries  ohez  1'hydrophile.     Bulletin 

Acad.  Roy.  de  Belgique.     Tome  XL.    1877. 
RENAUT.    Note  sur  les    disques  accessoires  des  disques  minces  dans  les  muscles 

strips.     Compt.  rend.    Tome  LXXXV.    No.  21.     1877. 
BIEDERMANN.     Zur  Lehre  vom  Ban  der  quergestreif ten  Muskelfaser.    Wiener  Acad. 

Sitzungsbericht.    Bd.  LXXXV.    No.  21.     1877. 
SCHAEPER.     Quain's  Anatomy.     Eighth  edition.     New  York:  Wm.  Wood   &  Co. 

1878. 
NASSE.     Zur  microscopischen  Untersuchung.  des  quergestreiften  Muskels.    Pfliiger's 

Archiv.     Bd.  XVII.     1878. 
FRORIEP.     Ueber  das  Sarcolemm  und  die  Muskelkerne.     Archiv  f  iir  Anatomic  und 

Entwickelungsgeschichte.    1878. 

ENGELMANN.      Nouvelles  recherches  sur  les  phenoinenes  microscopique  de  la  con- 
traction musculaire.      Archives  Neanderlaises  des  Sciences  exactes  et  natu- 

relles.     1878. 
FLEMMING.     Ueber  Formen  und  Bedeutung  der  organischen  Muskelzellen.      Zeit- 

schrift  fiir  wissenschaftliche  Zoologie.    XXX.     Supplement.    1878. 
UNGER.     Untersuchungen  iiber  die  quergestreiften  Muskelf asern  des  lebenden  Thiers. 

Wiener  medinische  Jahrbiicher.     1879.    (Largely  pathological.) 
NEWMAN.     New  Theory  of  Contraction  of  Striated  Muscle,  and  Demonstration  of 

the  Composition  of  the  Broad  Dark  Bands.     Journal  of  Anatomy  and  Physi- 
ology.    Vol.  XIII.    1879. 
CHITTENDEN.     Histochemische   Untersuchungen  iiber  das  Sarcolemm  und  einige 

verwandten  Membranen.    Untersuchungen  aus  der  Physiol.  Institut  der  Uni- 

versitat  Heidelberg.     Bd.  III.     1879. 
KLETN  and  SMITH.     Atlas  of  Histology.    Part  V.    1879-80. 
RANVIER.     Leqons  d'anatoraie  generate  sur  le  systeme  musculaire.    Paris,  1880. 


CHAPTER  XL 

THE  BLOOD-VESSELS. 

BY  EDMUND  C.  WENDT,  M.D., 

Curator  of  St.  Francis'  Hospital,  New  York  City,  etc. 

IN  man,  a  closed  circuit  of  branching  tubes,  which  proceed 
from  a  central  organ,  the  heart,  and,  ramifying  throughout  the 
body,  return  the  blood  to  this  central  organ,  constitutes  the 
blood-vascular  system,  as  it  has  been  named. 

Of  these  vessels  we  recognize  three  different  kinds :  arteries, 
capillaries,  and  veins.  The  arteries  convey  the  blood  to  the 
various  capillary  districts,  whence  it  is  again  collected  and  car- 
ried back  to  the  heart  by  the  veins. 

The  arteries,  highly  elastic  throughout,  are  composed  of 
three  superimposed  layers  or  tunics.  The  veins,  less  elastic, 
and  consequently  more  flaccid  and  compressible,  likewise  con- 
sist of  three  coats  or  tunics.  In  both  sets  of  vessels  these 
coats  have 'received  the  names  of  intima  for  the  inner,  media 
for  the  middle,  and  adventitia  for  the  external  layer.  The 
capillaries,  intervening  between  the  two,  form  minute  branch- 
ing tubules,  which  generally  have  but  a  single  exceedingly 
thin  and  permeable  membrane  as  the  sole  constituent  of  their 
walls. 

Of  course,  all  these  vessels  merge  into  one  another,  so  that 
a  sharp  line  of  demarcation  can  nowhere  be  drawn  ;  but  in 
their  typical  forms  they  present  clearly  defined  structural  dif- 
ferences, necessitating  a  separate  description  of  them.  We 
begin  with  the  simplest  and  yet  most  important  class : 

The  capillary  blood-vessels.— They  are  composed,  as  we 
have  already  said,  of  a  single  layer  of  cells,  arranged  in  tubu- 
lar form,  and  containing  nuclei.  These  corpuscles  are  di- 
rectly continuous,  on  the  one  hand,  with  the  inner  coat  of 


THE   BLOOD-VESSELS.  143 

the  terminal  arteries,  and,  on  the  other,  with  the  intima  of  the 
veins,  hence  also  with  the  lining  membrane  of  the  heart.  They 
are  called  endothelia,  and  since  they  constitute  the  only  struc- 
tural elements  which  enter  into  the  composition  of  all  blood- 
vessels, we  will  first  consider  them  and  their  relations  to  these 
vessels. 

The  vascular  endothelium. — Histologists  understand  by 
the  term  endothelium  a  thin  layer  of  flattened  cells  lining  the 
free  surface  of  various  membranes,  canals,  sheaths,  and  cavi- 
ties, all  belonging  to  the  serous  type.  Epithelium,  on  the 
other  hand,  is  found  covering  the  skin  and  mucous  surfaces. 
All  endothelia,  in  common  with  the  blood,  the  blood-vessels, 
and  connective  tissues,  are  derived  from  the  mesoblast,  or  mid- 
dle of  the  three  fundamental  layers  of  the  embryo.  The  epi- 
thelia,  it  will  be  remembered,  originate  in  the  two  other  layers, 
called  epiblast  and  hypoblast,  respectively — the  former  being 
the  superior  and  the  latter  the  inferior  layer  of  the  embryo. 

In  adult  human  subjects  the  vascular  endothelia  are  made 
up  of  thin,  polygonal,  sometimes  irregularly  pentagonal,  flat- 
tened cell-plates.  Most  of  the  elements  are  furnished  with  a 
rounded  or  ovoid  nucleus,  of  central  or  more  or  less  peripheral 
location  (Fig.  58).  Some  have  two  nuclei.  In  general,  the  cells 
are  somewhat  elongated  in  the  longitudinal  direction  of  the  ves- 
sel to  which  they  belong.  They  also  grow  slightly  narrower  as 
the  calibre  of  the  vessel  decreases.  Their  borders  are  serrated 
or  scalloped,  and  dove-tailed  into  one  another.  An  albuminoid 
substance,  ordinarily  invisible,  cements  their  adjoining  edges. 
This  substance  has  the  peculiar  property  of  effecting  an  ener- 
getic reduction  of  silver  nitrate.  Hence,  by  proper  manage- 
ment, the  outlines  of  each  individual  cell  may  be  made  visible 
as  a  black  zigzag  surrounding  a  nucleus.  Every  cell  represents 
a  plate-like  expanse  of  modified  protoplasm.  Remnants  of  this 
original  substance  may  be  seen  to  surround  the  nuclei  of  young 
vessels,  where  they  appear  in  the  shape  of  varying  quantities 
of  distinctly  granular  matter.  Klein  has  described  an  intra- 
cellular  network,  formed  by  plexuses  of  minute  fibrils,  and 
associated  with  a  second  denser  reticulum  within  the  nucleus, 
called  the  intranuclear  network.  Whatever  interpretation  we 
choose  to  give  these  minute  structures,  the  fact  of  their  exist- 
ence is  indisputable.  In  man,  however,  their  presence  is  not 
as  readily  demonstrable  as  in  animals. 


144 


MANUAL    OP    HISTOLOGY. 


An  isolated  endotlielial  cell,  when  tilted  up  on  its  edge,  pre- 
sents the  appearance  of  a  straight  or  curved  double  contour, 
with  a  central  thickening  corresponding  to  its  nucleus.  Viewed 
en  face,  we  observe  the  sinuous  outline  and  the  central  or  ec- 
centric nucleus,  with  its  surrounding  granules  of  protoplasm. 
The  shape  and  contour  of  endothelial  cells  are  subject  to  con- 


Fio.  58. — Endothelium  of  the  carotid  artery  of  man,  after  treatment  with  nitrate  of  silver:    a,  cells; 
6,  clearer,  c,  darker  intermediate  spaces ;  d,  intra-cellular  circular  and  spotted  markings.    Eberth. 

siderable  variations  in  the  different  vascular  districts.  Such 
differences  also  occur  in  the  same  district,  with  the  varying  de- 
gree of  expansion  or  contraction  of  the  particular  vessel  under 
observation. 

The  capillaries  proper. — In  point  of  wideness  of  distribu- 
tion, this  variety  of  blood-vessels  greatly  exceeds  all  others. 
Indeed,  the  capillaries  occupy  a  rank,  in  this  respect,  second 
only  to  the  connective- tissue  group  of  histological  struc- 
tures. As  regards  importance  to  the  economy,  it  will  only  be 
necessary  to  advert  to  the  vital  processes  of  nutrition,  secre- 
tion, respiration,  and  excretion,  to  recall  the  quality  and 
extent  of  their  physiological  usefulness.  Throughout  the 


THE    BLOOD-VESSELS. 


145 


body  l  capillary  plexuses  are  interposed  between  arteries  and 
veins,  which  constitute  a  series  of  conveying  and  returning 
tubes.  Thereby  the  direct  continuity  of  these  blood-channels 
is  established. 

It  is  in  these  intermediate  territories,  and  in  them  only,  that 
the  blood  serves  its  true  function  of  giving  and  taking.  True 
markets  of  exchange,  then,  these  capillary  districts,  where  the 
system  is  supplied  with  new  material,  and  in 
return  gets  rid  of  useless  or  even  deleterious 
by-products  of  tissue-life.  Hence,  the  para- 
mount importance  of  these  vessels  in  the 
maintenance  of  life  and  health.  Hence,  also, 
the  direct  practical  utility  of  knowing  their 
minute  anatomy'  and  physiological  dignity. 
Every  practitioner  of  medicine  will  see  the 
important  relation  this  branch  of  histology 
holds  to  pathology,  and  therefore  to  thera- 
peutics. At  the  same  time  we  should  not 
forget  that  the  role  played  by  the  capillaries 
in  the  system  is  normally  due  to  the  inherent 
mechanical  and  physical  properties  of  a  fine- 
ly elastic  animal  membrane,  rather  than  to 
any  specific  action  of  their  cellular  constitu- 
ents. 

Robin,  following  Henle's  example,  dis- 
tinguishes several  varieties  of  these  vessels.  It 
seems  to  me  proper  to  limit  the  term  capil- 
laries to  those  minute  tubules  which  are 
entirely  devoid  of  muscular  elements.  This 
corresponds  to  the  classification  adopted  by 
Yirchow,  Kolliker,  Eberth,  Ranvier,  Frey, 
and  others.  It  is  the  one  therefore  that  has  Plo  59._Arather  lanre 
generally  been  accepted,  and  is  both  simple  JP^fcSjJ'JJS^g^ 

and    locriral  membranous  and  nucleated 

iu  logical.  tunica  adventitia  Eberth> 

The  diameter  of  these  tubules  varies  from 
0.0045  to  0.0115  mm.    Their  structure  is  readily  understood. 
Examined  in  the  living  animal  with  a  high  power,  we  see  mere- 
ly a  delicate,  hyaline,  double-contoured  membrane,  having  an 

1  Hoyer  has  shown  that  a  direct  communication  of  arterioles  with  venules  occurs 
normally  in  the  tips  of  the  fingers,  the  matrix  of  the  nails,  the  tip  of  the  nose,  and 
various  other  parts. 
10 


146 


MANUAL    OF   HISTOLOGY. 


average  thickness  of  1  to  2  micro-millimetres  (0.001 — 0.002 
mm.).  This  membrane  forms  a  tubule,  the  parietes  of  which 
are  studded  at  intervals  with  rounded  or  oval  nuclei,  often 
containing  one  or  more  bright  nucleoli.  When  oval,  these  nu- 
clei have  their  long  axis  parallel  with  the  direction  of  the  ves- 
sel. Their  average  size  is  0.0056  to  0.0074  mm.  They  possess 
the  property  of  eagerly  imbibing  most  of  the  staining  fluids 
employed  in  histology,  and  of  resisting  the  action  of  dilute 
acids,  alkalies,  and  other  reagents.  (See  Fig.  59.) 

Besides  nuclei,  the  capillary  wall  contains  at  various  points 
peculiar  granules,  which  indicate  its  protoplasmic  nature.  In 
addition,  Strieker  and  Eberth  have  described  lateral  processes 
and  pointed  prolongations  jutting  out  from  the  parietes  of  the 


FIG.  60.— Capillaries  of  the  lungs  of  the  frog,  with  irregularly  dentated  cells :  a,  vascular  meshes. 
Eberth. 

capillary  tubes.  In  growing  tissue  these-are  readily  demonstra- 
ble, often  forming  thread-like  connecting  bridges  between  neigh- 
boring vessels  ;  at  a  later  period  they  are  hollowed  out  into 
true  capillaries.  The  shorter  sprouts  are  also  protoplasmic 
buds,  capable  of  further  development  into  similar  vessels.  (See 
Fig.  61.)  By  employing  weak  solutions  of  silver  nitrate,  the 
capillary- wall  may  be  shown  to  consist  of  variously  shaped 
areas,  each  one  corresponding  to  a  nucleated  cell.  They  are 
the  endothelia,  and  represent,  as  already  stated,  the  sole  essen- 
tial constituents  of  all  capillaries.  Their  form  varies  with  the 
calibre  of  the  vessel,  the  smaller  capillaries  being  composed  of 


THE    BLOOD-VESSELS. 


147 


corpuscles  which  are  comparatively  narrow,  the  larger  vessels 
having  broader  cells.  In  man  they  have  an  average  length  of 
0.0756—0.0977  mm.,  and  an  average  breadth  of  0.01—0.05  mm. 
The  intercellular  boundaries,  brought  out  as  dark  lines  by 
means  of  the  silver  salt,  frequently  exhibit  little  nodular  swell- 
ings. (See  Fig.  58.) 

In  addition  to  the  ordinary  endothelia,  we  find  smaller 
areas,  generally  without  nuclei ;  they  have  rounded  or  some- 
what dentate  contours, 
and  are  interposed  be- 
tween the  other  cells. 
Eberth  believes  that 
some  of  these  intercal- 
ated areas,  as  Auerbach 
has  called  them,  proba- 
bly correspond  to  por- 
tions of  strangulated  vas- 
cular cells.  It  is  more 
logical  to  regard  them  as 
the  remnants  of  an  in- 
complete endothelial  des- 
quamation,  a  process 
which  is  of  physiologi- 
cal occurrence  through- 
out the  blood-vessels. 
These  remaining  bits  are 
finally  destined  to  be- 
come quite  detached 
from  the  vascular  wall,  and  are  then  swept  away  by  the  rush 
and  flow  of  the  blood-current.  The  detached  portions  of  such 
endothelia  and  their  nuclei  appear  as  free  granules  in  the  blood, 
where  they  have  puzzled  many  observers,  and  have  been  vari- 
ously called  microcytes,  hcematoblasts,  etc.  From  this  descrip- 
tion it  is  plain  that  Cohnheim's  view,  that  these  spaces  are 
openings  or  stomata,  is  not  sustained.  True,  we  find  in  serous 
membranes  of  certain  animals  real  openings,  but  these  always 
appear  of  rounded  shape,  and  are,  to  say  the  least,  not  com- 
monly observed  in  human  blood-vessels.  This  statement  of 
the  case  does  not  militate  against  Cohnheim's  well-known 
views  that  the  corpuscles  emigrate  through  the  vessels,  for, 
remembering  the  protoplasmic  nature  of  the  endothelial  tubes, 


FIG.  61. — A,  A,  stellate  connective-tissue  cells  connected  by 
B,B,  delicate  protoplasmic  threads  to  C,C,  sprouts  of  endothe- 
lial tubes  ;  D,  protoplasm  connecting  two  capillaries  ;  B,  nu- 
cleus imbedded  in  a  primitive  sprout  of  protoplasm,  budding 
from  wall  of  capillary.  Specimen  prepared  by  silver  nitrate. 


148  MANUAL    OF   HISTOLOGY. 

we  can  readily  account  for  the  phenomena  in  question.  The 
capillary-wall  is  elastic,  extremely  thin,  and  permeable.  By 
virtue  of  these  qualities,  it  may  allow  the  passage  of  a  leu- 
cocyte or  colored  globule  through  its  substance  without  suf- 
fering a  permanent  breach  of  continuity. 

The  writer's  views  on  endothelial  desquamation  as  a  normal  process  of  physi- 
ological import  may  strike  the  reader  as  insufficiently  substantiated  by  known 
facts.  But  when  we  remember  that  similar  processes  have  been  actually  ob- 
served taking  place  under  the  microscope,  all  doubts  as  to  the  probability  of 
this  endothelial  desquamation  should  vanish.  The  author  refers  to  the  recent 
observations  of  Altmann  (Arch.f.  mikros.  Anat.,  Vol.  XVI.,  p.  111).  This  his- 
tologist  investigated  the  changes  which  take  place  in  the  serous  epithelium 
(i.e.,  endothelium)  of  the  exposed  frog's  mesentery.  Multiple  swellings  of  the 
endothelia  were  seen  to  occur ;  then  portions  of  these  cells  would  become  de- 
tached. Such  detached  bits  were  found  to  resemble  in  their  appearance  ordi- 
nary leucocytes.  But,  in  spite  of  this  apparent  breaking  up  of  the  endo- 
thelia into  these  nucleated  corpuscles,  they  often  retained  their  individuality 
unaltered.  The  production  of  bodies  resembling  leucocytes  from  endothelia 
has,  therefore,  been  actually  observed  in  connection  with  serous  membranes, 
and  vascular  desquamation  is  essentially  the  same  process. 

The  capillary  blood-vessels  occupy  the  interstitial  connec- 
tive tissue  of  organs,  without  entering  their  parenchyma  proper. 
Cartilage,  the  teeth,  the  hairs  and  nails,  the  cornea,  and  cer- 
tain structures  of  the  nervous  system  and  organs  of  special 
sense  are  devoid  of  capillary  supply. 

Most  of  the  larger  tubes  are  invested  by  a  delicate,  exter- 
nal, sheath-like  structure,  called  the  capillary  adventUia  or 
vascular  peritTielium.  It  is  composed  of  a  rather  close  net- 
work of  delicate  connective- tissue  fibrils.  Prolongations  of  pe- 
culiar stellate  cells,  which  clasp  the  capillary- tube,  may  some- 
times be  seen  to  join  these  fibrils.  (Fig.  62.)  Such  branching 
cells  are  also  encountered  at  some  distance  from  the  capillaries. 
They  show  delicate  processes,  which  may  anastomose  with  the 
offshoots  of  the  adventitial  corpuscles.  In  other  places  we 
only  find  external  plates  of  connective-tissue  cells  (Krause's  ino- 
blasts),  which  have  become  more  or  less  fused  with  the  capil- 
lary-wall. In  many  instances  the  perithelium  is  inseparable 
from  the  connective-tissue  stroma  surrounding  the  vessel. 

In  reference  to  the  manner  of  anastomosis,  the  forms  and 
modes  of  ramification  of  different  networks  vary  with  the  dif- 
ferent tissues  and  organs  of  the  body.  Hence,  a  simple  in- 


THE    BLOOD-VESSELS. 


149 


spection  of  capillary  reticula  will  generally  enable  us  to  decide 
the  nature  of  the  tissue  or  organ  in  question.  From  a  physio- 
logical point  of  view,  we  recognize  a  causal  relation  between 
high  capillary  development  and  great  functional  activity. 
Therefore,  the  abundance  of  capillaries  will  determine  the 
physiological  importance  of  an  organ. 

The  chief  forms  of  ramification  may  be  grouped  as  follows : 
1.  Loops  (a),  simple  or  compound;  e.g.,  the  skin  and  the  hard 


FIG.  62. — Capillaries  from  the  hyaloid  membrane  of  the  frog:  er,o,  capillary-wall;  6,6,  nuclei  of  the 
same;  c,c,  cells  of  the  tunica  ad  ventitia ;  rf,rf,  processes  of  these  cells  clasping  the  capillary-wall;  e,  stel- 
late cell  anastomosing  with  the  cells  of  the  tunica  adventitia.  Eberth. 

palate  ;  (b)  reticulated  (the  intestinal  villi).  2.  Tufts  (the  kid- 
ney). 3.  Irregularly  polygonal  networks  (the  glands  and  the 
mucous  membranes).  4.  Rounded  reticula,  with  round  or 
polygonal  meshes  (adipose  tissue).  5.  Reticula  with  elongated 
meshes  (the  muscles,  bones,  and  tendons).  There  would  be  a 
certain  satisfaction  in  knowing  that  this  or  that  vessel  had  a 
precise  breadth,  and  its  coat  a  certain  thickness.  The  precision 
would  be  apparent,  however,  rather  than  real,  because  such 


150 


MANUAL    OF    HISTOLOGY. 


measurements  vary  greatly  at  different  times  in  the  same  ani- 
mal, and  even  more  so  in  different  animals.  It  may  be  stated, 
in  general,  that  the  calibre  corresponds  to  the  size  of  the  largest 
blood-globules.  In  man,  therefore,  we  have  an  average  diam- 
eter of  about  0.007  mm.  The  largest  capillaries  exist  in  the 
mucous  membrane  of  the  stomach  and  colon,  the  periosteum 
and  bones,  and  the  pituitary  body.  The  smallest  are  found  in 
the  skin,  the  small  intestine,  the  lungs,  the  muscles,  the  gray 
substance  of  the  brain,  and  the  retina  (Valentin,  Weber,  and 
Henle). 

The  genesis,  reproduction,  and  regeneration  of  capillaries. 
—There  is  still  much  uncertainty  about  the  mode  in  which 
blood-vessels  are  first  formed  in  the  embryo.  My  personal 


FIG.  63. — Growth  and  development  of  capillaries  by  nucleated  sprouts  of  protoplasm :  A,  poly-nucle- 
ated large  sprout  with  filiform  process  ;  B,  B,  blood-globules  ;  C,  branched  cell ;  D,  delicate  protoplasmic 
tendril  linking  C  with  E,  a  smaller  mono-nucleated  sprout  of  endothelial  wall. 

observations  on  this  subject,  while  working  recently  under  the 
supervision  of  Kolliker,  appear  to  confirm  the  view  held  by 
Foster  and  Balfour.  These  authors'  account  of  the  interesting 
process  may  be  summed  up  as  follows  :  About  the  second  day 
of  incubation  in  the  chick,  certain  mesoblastic  cells  send  out 
solid  processes,  which,  uniting,  form  a  protoplasmic  network 
containing  nuclei.  A  majority  of  the  latter  acquire  a  reddish 
tint,  and  are  ultimately  transformed  into  colored  blood-glob- 
ules. Other  nuclei,  however,  remain  unaltered,  and,  receiving 
an  investment  of  protoplasm,  form  walls  inclosing  the  reddened 


THE   BLOOD-VESSELS.  151 

nuclei.  The  protoplasm  of  these  central  nuclei  rapidly  becomes 
liquefied,  thus  forming  the  blood-plasma.  And  now  we  have  a, 
system  of  communicating  tubules,  containing  corpuscles  float- 
ing in  a  plasma,  their  walls  consisting  of  nucleated  cells. 
Hence,  the  blood-vessels  do  not  arise  as  intercellular  spaces, 
but  are  hollowed  out  to  form  channels  in  an  originally  solid 
reticulum  of  protoplasm  derived  from  mesoblastic  cells. 

This  explanation  of  the  way  in  which  vessels  are  formed 
aids  us  in  understanding  both  how  capillaries  are  reproduced 
in  the  adult,  and  their  regeneration  under  pathological  condi- 
tions. The  capillary -wall  itself,  under  the  influence  of  favor- 
ing circumstances,  begins  to  bud,  as  it  were  ;  the  delicate  proto- 
plasmic sprouts  send  out  more  delicate  filaments,  which,  uniting 
with  similar  offshoots  from  neighboring  vessels,  establish  a 
connection  between  two  capillaries.  In  due  time  these  solid 
structures  undergo  the  familiar  process  of  hollowing  out,  and 
the  newly  formed  vessel  is  complete.  Frequently  the  proto- 
plasmic threads  communicate,  forming  a  reticulum  which  Ran- 
vier  has  called  vasoformative  network.  This  author  also  ob- 
served that  capillaries  develop  from  special  cells,  termed 
vasoformative  cells.  They  resemble  leucocytes,  and  form  by 
their  prolongations  a. network  of  solid  protoplasm.  This  is 
originally  quite  independent  of  already  existing  capillaries. 
Subsequently,  however,  a  consolidation  is  effected,  and  the 
blood  then  flows  through  these  new  channels  in  the  usual 
manner. 

The  author  has  been  able  to  trace  collections  of  emigrated 
leucocytes  through  various  stages  of  progressive  development, 
culminating  in  the  formation  of  true  capillaries.  The  experi- 
mental investigations  on  this  subject  were  carried  out  in  Pro- 
fessor v.  Hi ndfleisch's  laboratory,  and  have  been  fully  described 
by  his  former  assistant,  Dr.  Ziegler,  of  Wiirzburg. 

The  arteries. — If  we  follow  the  capillaries  in  a  direction 
toward  the  heart,  we  soon  find  the  endothelial  tube  receiving 
an  investment  of  unstriped  muscle-cells.  These  are  wound 
transversely  or  obliquely  around  the  capillary,  thus  forming  a 
second  tube,  as  it  were,  surrounding  the  first.  Externalto  the 
muscular  layer  there  appears  some  connective  tissue,  mingling 
with  which  elastic  elements  may  be  observed.  The  direction 
of  these  additional  fibres  is  mainly  longitudinal.  They  form 
the  third  or  external  coat,  called  the  adventitia,  the  second  or 


152 


MANUAL    OF   HISTOLOGY. 


middle  being  represented  by  the  muscle- cells,  and  the  first  or 
internal  by  the  endothelial  tube.  The  latter  now  receives  the 
name  of  intima.  When  the  layers  of  its  walls  are  arranged  in 
this  simple  manner  the  vessel  is  called  an  arteriole,  and  this 
constitutes  the  type  of  all  arteries. 

Arterioles,  however,  commonly  contain  a  few  additional 
fibres  between  the  intima  and  the  media,  as  the  first  indication 
of  what  afterward  becomes  a  special  layer.  This  structure, 
known  as  the  internal  elastic  coat,  attains  considerable  devel- 
opment in  the  larger  vessels.  With  the  growth  of  an  artery  in 
calibre  its  individual  coats  are  reinforced  by  additional  layers. 
Hence  the  thickness  of  the  entire  wall  increases  at  the  same 


l&Sssm 


FIG.  64.  FIG.  65.  FIG.  66. 

FIG.  64.— Minute  artery  showing  optical  section  of  alternate  groups  of  muscle-cells,  and  an  external  nu- 
cleated membrane,  representing  the  tunica  ailventitia. 

FIG.  65.— A,  intima ;  B,  delicate  internal  elastic  coat ;  E,  media  (as  in  Fig.  64) ;  D,  adventitia.  Arteriole, 
from  a  child's  mesentery. 

FIG.  66.— Elastic  internal  tunic  of  the  basilar  arteries. 

time  that  its  structure  is  rendered  more  complex.  But  new 
tissues  never  appear.  Moreover,  the  increased  thickness  is  not 
uniformly  proportionate  to  the  enlarged 'calibre  ;  neither  does  it 
take  place  by  equal  participation  of  the  different  tissues  men- 
tioned. In  vessels  of  small  and  medium  size  there  is  a  prepon- 
derance of  muscular  over  elastic  elements.  In  the  larger  trunks 
the  reverse  condition  obtains.  It  is,  therefore,  proper  to  dis- 
tinguish arteries  of  the  muscular  from  those  of  an  elastic  type. 
The  latter  class  is  represented  by  the  principal  distributing 
trunks,  all  the  remaining  arteries  belonging  to  the  muscular 
type.  There  exist,  however,  no  abrupt  lines  of-  demarcation 
between  these  main  forms— the  one  merging  gradually  into  the 
other. 

The  interposition  of  the  internal  elastic  coat  between  the 


THE    BLOOD-VESSELS. 


153 


intima  and  the  media  marks  the  transition  of  a  minute  into  a 
small  artery.  This  new  layer  consists  at  first  of  delicate  fibrils 
of  elastic  tissue,  or  an  apparently  homogeneous  membrane. 
Vascular  contraction  throws  it  into  folds,  which  appear  as 
longitudinal  striae  or  a  transverse  series  of  continuous  festoons. 
As  the  vessel  grows  larger  this  coat  gets  thicker,  becomes  dis 
tinctly  fenestrated,  and  presents  a  reticulat- 
ed appearance.  It  is  now  made  up  of  inter- 
lacing bundles  of  connective  tissue  and  elas- 
tic fibres,  with  spaces  left  between  them. 
The  latter  constitute  the  fenestrse  of  this 
layer,  which  in  the  large  vessels  becomes  a 
double  or  triple  lamellated  membrane.  Be- 
tween it  and  the  lining  endothelium  there 
appears  still  another  structure,  which  has  re- 
ceived various  names  from  different  authors. 
Thus,  Kolliker  has  called  it  the  striated  in- 
ternal  coat;  Remak,  the  innermost  longi- 
tudinal fibrous  coat ;  and  Eberth,  the  in- 
ternal fibrous  coat.  We  shall  employ  the 
last  term.  The  internal  fibrous  coat  consists 
at  birth  of  a  granular  substance,  which  be- 
comes distinctly  fibrillated  in  the  adult. 
Embedded  in  this  membrane  lie  numerous 
branching  corpuscles,  containing  large,  con- 
spicuous nuclei.  Besides  these  cells,  smaller, 
so-called  granulation-bodies  are  frequently 
seen.  So  far  from  regarding  them  as  of  path- 
ological origin  (Eberth,  in  ''Strieker's  His- 
tology"), I  prefer  to  consider  them  as  ma- 
trix-cells for  the  regeneration  of  desquamated 
endothelia.  My  reasons  for  so  doing  are 


Fio.    67.  —  Small    artery 


clei  of  the  tunica  adventitia; 
6,  muscle  nucleus ;  c,  elastic 
«TI  T        .  i         11         -i  i  internal  tunic :  d.  membrane 

as  follows :    In  the  blood-vessels  of  young   formed  of  fusiform 


Eberth. 


animals  and  newly  born  infants  I  have  fre- 
quently noticed  thick,  dark,  and  granular  bodies  immediately 
below  the  endothelial  lining.  These  subendothelial  cell-plates 
were  smaller  and  more  polyhedral  than  ordinary  endothelia, 
and  invariably  contained  one  or  even  two  nuclei.  They  ap- 
peared to  resemble  germinating  endothelial  cells,  such  as  Klein 
has  described  as  occurring  in  serous  membranes.  They  did 
not,  however,  occur  in  single  layers,  as  Klein  has  seen  them, 


154 


MANUAL    OF   HISTOLOGY. 


but  in  strata.  They  were  observed  in  particular  vessels  of 
young  animals.  It  seems  likely  that  these  cells  disappear  or 
shrivel  with  the  growth  of  the  individual,  but  their  sudden  reap- 
pearance in  pathological  processes  leads  the  author  to  believe 
that  at  least  some  of  them  persist  through  life.  Talma  ( Vir- 
cTiow's  Arch.,  Vol.  LXXVIL,  pp.  242-269)  observed  similar 
elements,  but  thinks  they  are  derived  from  the  ordinary  en- 
dothelia,  instead  of  vice  versa.  He  is  also  convinced  that  the 
latter  are  merely  modified  leucocytes  ;  but  this  view  has  been 
shown  to  be  erroneous  by  Virchow  (ArcTiiv  f.  path.  Anat., 
Vol.  LXXVIL,  pp.  380-383).  Endothelial  desquamation  is 
probably,  as  already  stated,  a  physiological  process  of  constant 


'<SP 


^    ©> 

-.^-,  ^,^:^,;,, 

-   ^      <s^    "  ,^ 

e,  ^/^^  1    m,b 


FlG.  68. — Transver-e  section  through  small  artery  and  vein :  A,  artery ;  a,  intima  with  bulging  en- 
dothelial  cells,  the  vessel  being  drawn  in  a  state  of  contraction  ;  ft,  internal  elastic  coat,  wavy  for  same 
reason ;  c,  media ;  d,  adventitia.  B,  vein,  same  denominations. 

occurrence,  and  in  some  respects  analogous  to  the  epithelial 
shedding  from  the  surface  of  the  skin  and  mucous  membranes. 
The  media  musculosa,  or  middle  coat,  consists  of  superim- 
posed layers  of  smooth  muscle-elements  disposed  in  groups. 
Most  of  them  lie  transversely  to  the  course  of  the  vessel.  The 
intervals  between  neighboring  groups  are  occupied  by  connec- 
tive tissue  and  elastic  fibres,  arranged  in  networks.  This  inter- 
stitial substance  becomes  augmented  with  the  increasing  calibre 
of  the  artery.  In  the  largest  trunks  it  all  but  replaces  the 
muscle-cells.  Here,  however,  the  elastic  fibres  also  reach  their 
maximum  development,  encroaching  upon  the  connective-tissue 
elements  until  the  latter  become  quite  inconspicuous.  Besides 
its  principal  transverse  layer,  the  media  also  contains  fusiform 
muscle-cells,  placed  in  an  oblique  or  longitudinal  direction. 


THE    BLOOD-VESSELS. 


155 


They  are  scattered  irregularly  throughout  the  middle  coat. 
Sometimes  the  intima  and  the  adventitia  also  contain  sparsely 
distributed  muscle-cells.  The  arterial  muscular  coat  is  dis- 
tinctly separated  from  the  intima  by  the  interposition  of  the 
internal  elastic  coat.  Externally  a  sharp  boundary  is  formed 
either  by  the  adventitia  or  by  the  external  elastic  coat.  The 
latter  appears  as  a  separate  membrane  in  arteries  of  small  and 
medium  size.  There  are,  however,  exceptions  to  this  rule.  The 
external  elastic  coat  consists  of  a  close  network  of  delicate 


FIG.  69.— Longitudinal  section  of  pulmonary  artery.  Mounted  in  glycerine  and  acetic  acid  after  de- 
siccation of  the  artery,  o,  Internal  portion  of  intima  ;  6,  external  portion  of  intima ;  c,  internal  elastic 
coat ;  d,  media,  showing  cross  sections  of  muscle  fibres  and  elastic  tissue  ;  e,  adventitia. 

elastic  fibrils,  anastomosing  with  similar  adventitial  reticula. 
The  adventitia  is  composed  of  interlacing  bundles  of  connec- 
tive tissue,  commingled  with  elastic  lamellae  of  varying  thick- 
ness. 

The  veins. — From  their  origin  in  the  capillaries  to  the  point 
where  they  enter  the  trunk  proper,  the  veins  preserve  through- 
out a  uniform  type  of  structure.  But  no  sooner  have  they 
penetrated  into  the  visceral  cavities  of  the  body  than  we  find 
them  undergoing  considerable  alterations,  which  may  either 
increase  or  diminish  the  complexity  of  their  structure  (Ran- 
vier).  The  veins  are  far  more  numerous  than  the  arteries. 
They  are  also,  as  a  rule,  wider  and  more  dilatable,  and  have 
thinner  coats.  It  is  owing  to  the  latter  peculiarity  that  the 


156 


MANUAL    OF    HISTOLOGY. 


color  of  the  blood  is  seen  through  their  semitranslucent  walls. 
Finally,  they  branch  more  frequently  than  the  arteries.  Three 
main  coats  or  tunics  enter  into  the  composition  of  most  veins. 

These  resemble  the  corre- 
sponding arterial  struc- 
tures, and  have  likewise 
received  the  names  of  in- 
tima,  for  the  internal  endo- 
thelial  lining  ;  media,  for 
the  middle  muscular  ;  and 
adventitia,  for  the  external 
connective-tissue  coat. 

Veins,   however,    differ 
from  arteries  in  the  feebler 
development  of  their  mus- 
cular coat,  in  the  compara- 
tive paucity  of  elastic  ele- 
ments,   a    greater    laxity 
of  their  intima,   and  the 
presence  in  some  of  valves. 
We  may  distinguish  veins  of  smaller  calibre,  or  venules, 
from  the  vessels  of  medium  and  large  size.      The  venules,  like 
the  arterioles,  in  certain  respects  resemble  the  capillaries.     As 


FIG.  70.— Portion  of  innominate  vein  of  dog,  after  in- 
jection of  a  solution  of  silver  nitrate.  The  endothelial 
cells  and  their  nuclei  are  visible.  The  media  shines 
through  this  layer. 


B    S 


FIG.  71. — Arteriole  and  vennle  from  child's  mesentery,  treatment  by  acetic  acid  and  glycerine:  A,  ar- 
tery ;  a,  nucleus  of  muscle-cell  of  media  ;  ft,  same  in  transverse  section  (optical).  B,  vein  ;  c.  nucleus  of 
connective  tissue  constituting  media,  which  in  these  minute  veins  contains  no  muscle-cells ;  tf,  nucleated 
connective  tissue. 

it  may  become  important  to  differentiate  the  minuter  forms 
of  vessels,  we  will  here  briefly  indicate  the  main  points  of  dis- 
tinction between  full-sized  capillaries,  small  veins,  and  arte- 


THE    BLOOD-VESSELS. 


157 


rioles.     In  the  latter,  the  endothelial  cells  are  more  nearly 

fusiform,  longer,  and  somewhat  narrower  than  in  the  venules. 

In  the  capillaries,  their  form  and  dimensions  hold  an  interme- 

diate position  between  the  arterial  and  venous  types.     The 

middle  coat  is  entirely  wanting  in  capillaries,  and  is  much  less 

conspicuous  in  the  small  veins  than  in  the  arterioles.     In  fact, 

under  ordinary  circumstances,  the  muscle-coat  forms  by  far  the 

most  characteristic  distinguishing  feature  between  these  ves- 

sels.   Venules  quite  frequently  have  only  a  few  sparsely  scat- 

tered muscle-cells,  in  place  of  the  continuous  muscular  layer 

which  exists  in  minute 

arteries.      The    former 

also  are  either  altoge- 

ther deficient  in  the  in- 

ternal elastic  coat,  or  the 

presence  of  this  struc- 

ture is  barely  indicat- 

ed by  delicate  elastic 

fibres  ;  these  latter  usu- 

ally have  a  longitudinal 

direction.    On  the  other 

hand,  arteries  of  corre- 

sponding   calibre    are 

mostly  furnished  with 

a  distinct  elastic  inner 

coat.     Finally,  with  re- 

S*ard  tO    the    adventitia 

we  find  it  more  highly 
developed  proportionally  in  venous  than  in  arterial  vessels, 
whereas  capillaries  commonly  have  only  a  few  faint  fibres  to 
denote  the  presence,  in  them  also,  of  this  coat. 

The  internal  elastic  coat  of  the  larger  and  largest  veins  is 
very  feebly  developed  in  comparison  with  that  of  the  arteries. 
Distinct  fenestrated  membranes  are  scarcely  ever  encountered. 
Veins  are  likewise  possessed  of  an  internal  fibrous  layer,  but 
here  again  we  observe  that  comparatively  feeble  development 
of  a  coat  which  in  the  arteries  is  quite  conspicuous. 

Among  the  many  special  characteristics  of  the  various 
veins  in  different  regions,  we  will  only  mention  the  following  : 
the  jugular  veins  show  well-marked  elastic  reticula,  the  meshes 
of  which  contain  sparse  muscular  elements.  In  the  femoral, 


FIG.  72.  —  Longitudinal  section  of  popliteal  vein  :  r/,  tritium  ; 


158  MANUAL    OF    HISTOLOGY. 

brachial,  and  subcutaneous  branches  there  is  a  media  of  con- 
siderable dimensions.  The  inferior  vena  cava  has,  in  addition 
to  a  transverse  layer  of  muscle-cells,  a  longitudinal  one  of 
greater  thickness,  and,  besides  these,  contains  muscle-cells, 
which  are  scattered  through  its  elastic  coat.  The  veins  of  the 
meninges  of  the  encephalon  and  cord,  the  retina,  the  bones, 
and  the  muscles,  and  the  jugular,  the  subclavian,  the  innomi- 
nate, and  the  thoracic  portion  of  the  vena  cava  are  all  entirely 
devoid  of  a  true  muscular  coat.  The  veins  of  the  gravid  ute- 
rus have  only  longitudinal  muscle-elements.  In  addition  to  an 
outer  longitudinal  layer,  the  vena  cava,  the  azygos,  the  renal, 
the  hepatic,  the  internal  spermatic,  and  the  axillary  veins  pos- 
sess an  inner  circular  layer.  The  iliac,  the  femoral,  the  popli- 
teal, and  several  other  veins  contain  a  middle  coat  of  transverse 
muscle-cells,  between  internal  and  external  longitudinal  layers. 

The  valves  of  the  veins  consist  of  longitudinal  bundles  of 
connective  tissue  commingled  with  scanty  elastic  fibrils,  and 
containing  nucleated  cells.  The  inner  endothelial  layer  appears 
to  be  a  direct  continuation  of  the  intima  of  the  vein.  That 
portion  of  the  subendothelial  tissue  which  does  not  face  the 
blood-current  is  less  developed  than  the  part  turned  toward  it ; 
the  elastic  fibres  of  the  latter  are  also  barely  visible.  The  at- 
tached valvular  border  frequently  presents  transversely  dis- 
posed muscle-elements.  Eberth  has  denied  their  occurrence, 
but  they  have  been  repeatedly  observed  by  Banvier  and  other 
competent  histologists. 

Peculiar  vascular  structures. — The  following  structures  are 
remarkable  for  the  conspicuous  and  characteristic  development 
of  their  blood-vessels  the  vascular  membranes,  tunicw  vascu- 
losce,  such  as  the  pia  mater  of  the  brain  and  spinal  cord,  and 
the  choroid  coat  of  the  eye.  In  these  we  find  that  the  excessive 
vascularity  is  intended  to  nourish,  not  the  membranes  them- 
selves, but  the  organs  which  they  invest. 

Blood-vascular  glands,  vascular  plexuses. — In  man,  two 
bodies  of  peculiar  structure  represent  this  group.  They  are 
the  coccygeal  gland  of  Luschka,  and  a  rudimentary  organ 
called  the  inlercarotid  gland.  Both  consist  essentially  of  con- 
voluted blood-vessels  and  nerves,  imbedded  in  a  nucleated  con- 
nective-tissue stroma.  The  coccygeal  gland  is  a  small,  rounded, 
pinkish  body,  of  rather  firm  consistence,  and  is  connected  by  a 
pedicle  with  the  middle  sacral  artery.  This  pedicle  contains 


THE    BLOOD-VESSELS. 


159 


blood-vessels  and  nerves.  The  arteries  entering  the  gland-like 
body  become  convoluted,  and  show  numerous  tubular,  fusi- 
form, or  ampullar  dilatations.  Sometimes  they  have  terminal 
sacculi,  closely  resembling  minute  aneurisms,  and  giving  the 
organ  its  glandular  appearance.  Indeed,  Luschka  has  called 
them  gland-tubules  and  vesicles.  After  death  they  are  com- 


Fio.  73.— Section  of  a  naturally  injected  coccygeal  gland :  a,  vessels  ;  B,  collection  of  cells.   Eberth. 

monly  found  to  be  empty,  but  by  proper  management  a  good 
natural  injection  with  blood  may  be  readily  obtained.  Both 
capillaries  and  veins  also  present  lateral  varicosities,  studding 
them  in  great  number.  All  these  vessels  have  the  usual  endo- 
thelial  lining.  External  to  this  there  appear  aggregations  of 
rounded  or  polygonal  cells.  They  are  furnished  with  nuclei, 
and  receive  an  investment  corresponding  to  the  vascular  ad- 


160 


MANUAL    OF    HISTOLOGY. 


a  - 


ventitia,  but  containing  comparatively  more  nuclei  than  that 
structure. 

The  inter  carotid  gland  differs  from  the  coccygeal  in  its 
larger  size,  and  because  it  contains  accumulations  of  ganglionic 
nerve-cells.  These  are  derived  from  the  carotid  plexus.  Here 
the  vascular  sacculi  also  more  nearly  resemble  dilated  capilla- 
ries, whereas  in  the  other  body  they  approach  the  arterial  type. 
In  all  other  respects  the  structure  of  these  vascular  plexuses 
is  identical.  Some  authors  regard  the  spleen  and  the  supra- 
renal capsule  as  belonging  to  this  group  of  blood-vascular 
glands.  The  author  sees  no  necessity  for  so  considering  them, 

and  the  subject  may 
therefore  be  dis- 
missed without  fur- 
ther comment. 

Corpora  caverno- 
sa. — They  consist  in 
great  part  of  dilated 
blood-vessels,  chief- 
ly of  the  venous 
type.  These  inter- 
communicate very 
freely,  and  when 
filled  with  blood 
cause  the  organ  to 
assume  the  peculiar 
condition  known  as 

erection.  The  penis  and  the  clitoris  are  supplied  with  caver- 
nous bodies.  The  urethra  of  the  female  and  the  vestibule  also 
contain  them.  Interlacing  bundles  of  muscle-fibres,  together 
with  similar  bands  of  connective  tissue,  form  a  framework  for 
the  support  of  the  vascular  structures  mentioned.  The  latter 
present  the  ordinary  endothelial  lining. 

Several  years  ago  Dr.H.  J.  Bigelow  succeeded  in  demon- 
strating the  existence  of  cavernous  tissue  in  the  nasal  fossae. 
In  a  letter  to  the  author,  Dr.  Bigelow  states  that  his  point 
was  "  the  demonstration  of  an  abundant  and  true  cavernous 
structure  and  erectile  tissue  on  and  about  the  turbinated  bones, 
occupying  the  place  of  what  had  been  previously  supposed  to 
be  only  venous  sinuses,  the  loops  of  Kohlrausch.  The  new  re- 
sult obtained  was  due  to  a  different  mode  of  preparation.  Kohl- 


pIG.  74.— A,  cellular  vascular  sheath,  from  the  coccygeal  plexus : 
a,  connective  tissue  with  scattered  cells  f  nd  nuclei ;  fc,  round  and 
polygonal  cells  lying  immediately  upon  the  capillary  wall,  c ;  B,  a 
capillary  from  the  coccygeal  plexus,  with  a  vascular  sheath  very  rich 
in  cells.  References  as  in  A.  Eberth. 


BIBLIOGRAPHY.  161 

rausch  injected  from  the  jugular  vein  ;  I  [Dr.  Bigelow]  inflated 
the  tissue  locally,  as  if  it  were  in  the  penis." 

Vasa  vasorum,  lymphatics,  and  nerves. — Nutrient  ves- 
sels are  found  in  the  walls  of  all  the  larger  arteries  and  veins, 
where  they  occupy  the  adventitia.  Sometimes  they  are  seen 
to  dip  down  into  the  outermost  portions  of  the  media.  Lym- 
phatics occur  as  clefts  or  spaces  between  the  various  tissues  of 
all  arterial  and  venous  trunks.  Some  vessels  are  ensheathed 
by  a  lymphatic  membrane,  which  is  sometimes  furnished  with 
a  lining  endothelium.  Such  structures  are  called  perivascular, 
or,  better,  circumvascular  spaces.  They  may  be  found  in 
connection  with  the  omental  and  the  mesenteric  vessels,  also 
the  splenic  and  the  hepatic  arteries,  as  well  as  certain  menin- 
geal  vessels  of  the  brain  and  cord. 

Nerve-fibres  are  seen  to  pass  to  many  of  the  blood-vessels. 
They  enter  the  adventitia,  and  at  its  internal  boundary  sud- 
denly appear  to  divide  into  numerous  filaments,  the  ultimate 
distribution  of  which  has  not  hitherto  been  satisfactorily  ascer- 
tained. They  seem  to  terminate  in  the  muscle-cells  of  the 
media.  Beale  considers  the  presence  of  ganglion-cells  in  the 
vascular  nerves  as  of  constant  occurrence.  The  author  cannot 
admit  the  truth  of  this  general  statement,  having  discovered 
such  cells  in  only  exceptional  instances.  There  is  no  discerni- 
ble difference  of  structure  between  the  vaso-constrictor  and  the 
vaso-dilator  nerve-fibres. 


BIBLIOGRAPHY. 

In  addition   to  the  well-known  standard  treatises  by  Bichat,   Kolliker,  Henle, 
Sappey,  Krause,  Frey,  Leydig,  Teichmann,  Strieker,  Klein,  Ranvier,  Donders,  Vier- 
ordt,  Luschka,  Pouchet  et  Tourneux,  the  following  may  be  consulted : 
LUDWIG.     De  arteriarum  tunicis.     Lipsiae,  1739. 
RAUSCHEL.     De  arteriarum  et  venarum  structura.     Vratisl.,  1830. 
EOBIN.     Sur  la  structure  des  arteres.    Compt.  rend.     1847. 
SCHULTZE.     De  art.  struct.     Gryph.,  1850. 

REMAK.     Hist.  Bemerk.  ueber  d.  Blutgefasswande.     Mailer's  Arch.,  p.  96.    1850. 
SEGOND.     Syst.  capillaire  sanguin.     Th£se.     Paris,  1853. 
REMAK.     Entwickelung  d.  Wirbelthiere.     Berlin,  1855. 
REMAK.     Klappend.  Venen.     Deut.  Klinik.     1856. 
HACKEL.     Muller's  Arch.     1857. 
LUSCHKA.     Virch.  Arch.    XVIII..  p.  106.     1860. 
11 


162  MANUAL    OF   HISTOLOGY. 

HOYER.     Arch.  f.  Anat.,  p.  244.     1865. 

KLEBS.     Virch.  Arch.     VoL  XXXII.,  p.  172.     1865. 

AEBY.     Med.  Cent.  Zeit.     No.  XIV.     1865. 

CHRZONSZCZEWSKY.    Virch.  Arch.     Vol.  XXXV.     1865. 

EBERTH.     Virch.  Arch.     Vol.  XLIII.,  p.  136,  and  Centralblatt,  p.  195.     1865. 

AUERBACH.     Virch.  Arch.     Vol.  XXXIII.     1865.     Med.  Cent.  Zeit.     No.  X. 

GIMBERT.      Structure  et  texture  des  arteres.     These.      Paris,  1865.     Journ.  de 

1'anat.  et  de  la  phys.     Kobin,  p.  536.     1865. 
FASCE,  LUIGI.     Istologia  della  arterie.     Palermo,  1865. 
LANGHANS.    Virchow's  Arch.    Vol.  XXXVI. ,  p.  197.    1866. 
His.     Die  Haute  uud  Hohlen  d.  Korper's.     Basel,  1866. 
LEGROS.     Journal  de  1'anat.  et  de  la  phys.     No.  III. ,  p.  275.     1868. 
TOLUBEW.    Beitr.  z.  Kennt.  d.  Baues  u.  d.  Ent  d.  Capill.    Arch.  mikr.  Anat.,  p. 

49.     1869. 

ZIEGLER.     Exp.  Unt.  ueber  d.  Herk.  d.  Tuberkelelemente.    Wurzburg,  1875. 
ZIEGLER.     Unt.  ueber  pathol.  Bind.  u.  Gefassneubildg.     Wurzburg,  1876. 
KOLLIKER.     Entwickelungsgeschichte.     Leipzig,  1876. 
DISSE.     Arch.  f.  mikros.  Anat.     Vol.  XVI.,  p.  1.     1879. 
ILLTMANN.    Arch.  f.  mikros.  Anat.    Vol.  XVI.,  p.  111.     1879. 


CHAPTER  XII. 

THE  LYMPHATIC  SYSTEM. 
BY  DR.  W.  R.  BIRDS  ALL,  NEW  YORK  CITY. 

HISTOLOGICAL  research  has  brought  to  light  within  recent 
years  no  more  important  or  interesting  facts  than  those  con- 
nected with  the  lymphatic  system ;  interesting,  in  exhibiting 
entirely  new  features  in  tissues  which  had  previously  been 
carefully  studied ;  and  important  in  their  physiological,  and, 
particularly,  in  their  pathological  relations. 

Assisted  by  experimental  pathology,  it  is  still  in  this  direc- 
tion that  we  are  to  look  for  advancement  in  pathological  his- 
tology, for  there  can  be  no  doubt  that  heretofore  too  little, 
attention  has  been  paid  to  the  lymphatic  system,  both  in  its 
histological  details  and  in  its  topographical  anatomy. 

Present  condition  of  the  mews  on  the  structure  of  the  lym- 
phatic system — Relations  to  the  connective  tissues. — Unfor- 
tunately we  have  still  a  great  variety  of  contradictory  observa- 
tions, and  various  interpretations  of  the  same  observations. 
Through  this  maze  of  uncertainties  it  is  not  easy  to  lead  the 
student  to  a  settled  opinion,  nor  can  all  the  phases  of  this  many- 
sided  subject  be  presented.  It  shall  be  our  aim,  however,  to 
draw  the  outlines.  If  the  student  wishes  to  follow  out  the 
controversies,  he  will  be  aided  by  the  references  which  are 
appended  to  this  chapter. 

It  may  be  said  that  we  have,  to  a  great  extent,  returned  to 
the  views  of  the  older  anatomists  and  physiologists,  and  be- 
lieve that  the  whole  connective- tissue  formation  is  a  network  of 
channels ;  that  its  interstices  are,  directly  or  indirectly,  con- 
nected with  the  lymphatic  capillaries  and  larger  vessels  ;  that, 
in  short,  the  lymphatic  system  is  pre-eminently  a  connective- 
'tissue  circulatory  system,  irregularly  distributed,  it  is  true,  but 


1G4  MANUAL    OF   HISTOLOGY. 

found  in  one  form  or  another  wherever  this  tissue  exists,  and 
constituting  in  the  serous  membranes  a  great  absorbent  sys- 
tem, with  its  special  connections,  the  lacteals,  the  lymphatic 
nodes  or  glands,  and  the  fat-tracts.  The  important  patho- 
logical processes,  both  acute  and  chronic,  connected  with  these 
membranes  are  due  principally  to  the  fact  that  they  are  parts 
of  this  great  lymphatic  system. 

Of  course  we  must  not  lose  sight  of  the  connections  of  the 
latter  with  the  complimentary  blood-vascular  system  ;  the  ten- 
dency has  been  too  much  in  the  opposite  direction,  however, 
and  this  more  extensive,  though  less  visible,  system  has  been 
too  often  neglected  in  favor  of  its  more  prominent  companion, 
in  the  consideration  of  processes  of  nutrition  and  of  patho- 
logical changes. 

General  histology  of  the  lymphatic  system  —  Previous 
ideas. — In  describing  the  lymphatic  system,  only  its  general 
histology  will  be  considered,  the  details  of  its  special  distribu- 
tion and  arrangement  being  classed  with  the  description  of  the 
different  organs  with  which  it  is  associated.  Since  the  serous 
membranes  have  come  to  be  regarded  as  important  parts  of  the 
lymphatic  system,  being,  in  fact,  great  membranous  expansions 
of  that  system,  they  are  naturally  and  easily  considered  in  con- 
nection with  each  other.  It  is  not  intended  to  treat  of  them 
here  in  their  special  details,  but  merely  to  make  a  general  his- 
tological  study  of  them  as  a  class.  It  is  convenient  to  begin 
with  them  in  taking  up  the  study  of  the  origin  of  the  lymphatic 
system. 

With  Yirchow  originated  the  theory  that  the  starting-point 
of  the  lymphatics  is  from  hollow  anastomosing  cells,  the  con- 
nective-tissue cells,  whose  prolongations  communicate  to  form 
continuous  tubes.  He  termed  them  plasma  cells.  Kolliker 
supported  this  doctrine,  and  a  similar  view  was  held  by  Ley- 
dig.  Henle  held  a  different  opinion,  whilst  Briicke  and  Ludwig 
reverted  to  the  ancient  theory  of  Bichat,  that  the  interstitial 
spaces  of  the  connective  tissue  are  the  true  sources  of  the  lym- 
phatics. Recklinghausen,  introducing  nitrate  of  silver  as  a 
reagent,  showed  that  the  lymphatic  vessels  are  lined,  and  the 
serous  membranes  covered,  with  flat  cells,  forming  an  endo- 
thelial  layer.  He  observed  the  passage  of  milk  and  fine  gran- 
ules, through  openings  in  the  central  tendon  of  the  diaphragm, 
from  the  peritoneal  to  the  pleural  surface.  He  believed  also 


THE    LYMPHATIC    SYSTEM.  165 

that  lie  had  discovered  a  system  of  canaliculi  in  connective  tis- 
sue, which  he  termed  sap  or  juice  canaliculi  (saftkanalchen). 
His  views,  as  modified  somewhat  later,  are,  that  the  connective 
tissue  is  traversed  by  serous  canaliculi  or  plasmatic  channels 
which  are  directly  continuous  with  the  lymphatic  vessels. 
"Not  mere  fissures  in  the  connective  tissue,  but  interstices  of 
the  fibrous  fasciculi  and  lamellse  of  connective  tissue,  cemented 
to  one  another  by  a  tenacious,  homogeneous,  firm  material,  in 
which  the  serous  canaliculi  are  buried." 

The  lymphatics  of  the  mesentery. — A  portion  of  the  mesen- 
tery between  the'trabeculse,  taken  fresh  from  a  cat  and  stained 
with  nitrate  of  silver,  exhibits  on  both  surfaces  an  endothelial 
layer,  the  cells  of  which  possess  an  irregular  outline,  marked 
by  the  deposit  of  silver,  either  in  a  supposed  intercellular  sub- 
stance or  in  crevices  between  the  cells.  Sometimes  this  outline 
is  polygonal,  sometimes  sinuous,  crenated,  or  even  sharply  den- 
tated.  It  may  be  an  even,  fine  line,  or  it  may  possess  irregu- 
larities as  if  beaded.  At  the  union  of  these  lines,  that  is,  where 
two  or  more  cells  terminate,  a  round,  irregularly  triangular,  or 
spindle-shaped  spot  may  be  often  observed,  which  is  stained 
like  the  intercellular  line,  or  in  a  lighter  or  darker  shade. 
There  are  other  spots  of  larger  size,  presenting  the  appearance 
of  openings  ;  we  shall  refer  to  them  again.  The  surface  of  the 
cells  may  be  clear,  or  granular,  sometimes  it  is  quite  dark,  vary- 
ing with  the  degree  of  staining  and  the  condition  of  the  tissue  ; 
a  nucleus  can  usually  be  seen  at  a  slightly  deeper  level.  This 
is  plainly  visible  in  unstained  or  slightly  stained  specimens,  or 
where  special  reagents  have  been  used  to  make  the  nuclei  promi- 
nent, as  hsematoxylin  or  picro-carminate  of  ammonia.  The 
granular  appearance  spoken  of  is  sometimes  confiiled  to  a  series 
of  cells  which  surround  a  stoma,  or  the  black  spots  mentioned, 
while  the  neighboring  cells  may  be  clear ;  in  other  cases,  sev- 
eral corpuscles  in  the  form  of  an  irregular  tract  may  present 
this  appearance. 

Klein  has  observed  cells  which  are  club-shaped,  undergoing  a  budding  pro- 
cess, i.e.,  giving  off  little  bodies  resembling  lymphoid  corpuscles.  He  has  given 
the  term  germinating  endothelium  to  these  cells.  Other  histologists  have  made 
similar  observations. 

Underneath  and  around  the  nuclei  a  delicate,  intricate,  re- 
ticulum  of  elastic  fibres  may  be  seen  plainly  in  unstained  speci- 


166  MANUAL    OF   HISTOLOGY. 

mens,  and  by  careful  focussing  in  silver  preparations.  Accord- 
ing to  Ranvier,  they  are  connected  near  their  point  of  union 
by  a  very  thin,  elastic,  fenestrated  membrane.  Below  the  layer 
of  elastic  fibres  is  the  connective  tissue  which  forms  the  basis 
of  the  membrane.  It  consists  of  fasciculi,  which  are  straight, 
or  wavy,  according  to  the  degree  of  tension  of  the  membrane, 
or  its  fasciculi  are  held  together  by  the  elastic  fibres,  which 
penetrate  from  the  reticulum  on  each  side.  They  usually  pre- 
-sent  a  decidedly  convoluted  appearance  in  ordinary  specimens, 
and  in  consequence  of  the  contiguous  fasciculi  not  possessing 
corresponding  convolutions,  clear  interspaces  are  seen.  Some- 
times the  fibres  are  very  irregular  in  their  arrangement.  Ran- 
vier claims  that  an  interfascicular  membrane  can  be  demon- 
strated here  also.  Ordinary  flat,  branching  connective-tissue 
cells  are  distributed  through  this  tissue ;  they  lie  upon  and 
between  the  fasciculi ;  they  are  particularly  numerous  under 
the  endothelial  layer.  Lymphatic  and  blood- capillaries  trav- 
erse the  interspaces  and  run  upon  the  fasciculi.  In  the  mesen- 
tery and  pleura  they  form  a  wide -meshed  plexus  ;  in  the  peri- 
cardium a  close  plexus. 

To  see  the  features  of  the  deeper  portions  to  advantage,  we 
must  remove  the  superficial  endothelial  layer  before  staining 
with  silver. 

Kleirts  method  of  studying  the  omentum. — Klein  has  de- 
scribed a  very  careful  process  for  doing  this,  and  as  he  claims 
it  must  be  followed  in  detail  to  obtain  the  results  at  which  he 
has  arrived,  we  reproduce  it :  "To  prepare  the  omentum,  a  rab- 
bit is  killed  by  bleeding  ;  the  stomach  is  exposed  ;  after  having 
pushed  the  intestine  to  the  right  side,  the  free  surface  of  the 
omentum  is  pencilled  several  times  from  the  large  curvature 
toward  the  diaphragm,  with  a  fine  camel's-hair  pencil  moistened 
with  fluid  of  the  abdominal  cavity.  After  that,  a  J  or  \  per 
cent,  solution  of  nitrate  of  silver  is  allowed  to  flow  over  the 
omentum  from  a  large  capillary -tube  until  the  membrane  has 
become  slightly  milky  (one  or  two  minutes  are  generally  suffi- 
cient) ;  after  that,  the  stomach,  together  with  the  omentum, 
spleen,  pancreas,  and  a  portion  of  the  duodenum  is  cut  out  and 
transferred  to  a  large  capsule  with  distilled  water  ;  after  some 
time  the  water  is  renewed  and  the  omentum  is  separated  under 
water,  together  with  the  spleen  and  pancreas,  from  the  stomach, 
with  scissors,  and  is  transferred  to  common  water.  Those  parts 


THE    LYMPHATIC    SYSTEM.  167 

of  the  omentum  which  are  seen  to  contain  small  patches  are  cut 

out  and  mounted A  failure  is  more  frequent  than  a 

success.  Either  the  surface  has  not  been  pencilled  enough, 
and  then  the  endothelium  of  both  surfaces  is  colored,  and 
consequently,  hardly  anything  is  to  be  seen  of  the  cellular 
elements  of  the  ground-substance ;  or  the  surface  has  been 
pencilled  too  hard,  and  then  the  arrangement  of  the  ground- 
substance  is  altered,  its  bundles  appear  considerably  stretched 
and  distinctly  fibrillar." 

When  these  patches  referred  to,  found  in  the  mesentery, 
and  particularly  in  the  omentum,  are  examined,  they  are  ob- 
served, according  to  Klein,  to  consist  of  systems  of  somewhat 
flattened,  finely  granular,  nucleated,  branched  corpuscles  con- 
nected together  ;  the  spaces  which  appear  clear  between  them 
forming  the  lacunae  and  canaliculi,  corresponding  to  Reckling- 
hausen's  lymph  canalicular  system.  The  nuclei  of  these  cells 
are  sharply  defined,  oval,  and  possess  one  or  two  nucleoli. 
Lymphoid  corpuscles  are  found  in  these  spaces,  and  also 
slightly  larger  corpuscles,  which  are  supposed  to  be  derived, 
in  part,  at  least,  from  the  branched  cells  by  a  process  of  bud- 
ding. Klein  calls  these  patches  lympTiangeal  patches  or  nod- 
ules,  and  lympTiangeal  tracts.  He  divides  them  into  two 
classes. 

The  perilympliangeal  nodules  or  tracts  which  lie  closely 
connected  with,  but  principally  outside  of,  the  lymphatic  ves- 
sels, are  accumulations  of  more  or  less  flat,  branched  cells, 
which,  by  their  growth  and  proximity  to  one  another,  make  the 
canaliculi  shorter  or  close  them  entirely.  The  second  class  de- 
velop within  the  lymphatic  vessels,  and  are  termed  endolym- 
pJiangeal  nodules  or  tracts.  They  consist  of  those  which 
perfectly  resemble  adenoid  or  reticular  tissue,  and  those  which 
are  formed  of  a  reticulum  of  branched  cells,  their  spaces  being 
filled  with  liquid  or  a  few  lymphoid  corpuscles.  The  last  form 
may  have  a  rich  blood-capillary  plexus,  and  the  branched  cells 
may  possess  buds,  pedunculated  and  non-pedunculated,  sup- 
posed to  represent  different  stages  in  the  formation  of  a  lym- 
phoid corpuscle.  These  tracts  and  nodules  are  found  most 
frequently  in  the  neighborhood  of  the  blood-vessels  and  trabe- 
culse.  In  young  animals  they  are  much  less  numerous  and 
more  isolated  than  in  adults,  where  they  have  become  fused 
into  extensive  tracts  in  consequence  of  the  growth  and  division 


168  MANUAL    OF    HISTOLOGY. 

of  the  branched  cells.  Ranvier  has  described  similar  struc- 
tures under  the  name  "laches  laiteuses." 

Development  of  fat-tissue. — Their  relation  to  the  develop- 
ment of  fat-cells  is  of  extreme  interest.  If  we  accept  the  views 
of  Klein  and  Flemming,  the  branched  cells  are  converted  into 
fat-cells,  and  the  former  observer  has  pointed  out  that,  by  fol- 
lowing up  a  perilymphangeal  tract  into  a  vascularized  fat-tract, 
we  may  find  all  stages  of  conversion  into  fat-tissue.  The  fat- 
tracts  are  found  in  the  same  location  as  the  perilymphangeal 
tracts,  that  is,  along  the  larger  blood-vessels,  and  the  greater 
the  number  of  the  former  the  less  there  are  of  the  latter.  The 
conversion  of  branched  cells  into  fat-cells  varies  in  different 
animals,  and  in  different  membranes  of  the  same  animal,  and 
under  different  conditions  of  nutrition.  The  formation  of  lym- 
phoid  corpuscles,  supposed  to  go  on  from  the  branched  cells, 
must  cease,  necessarily,  when  they  become  converted  into  fat- 
cells,  and  it  is  found  that  they  are,  in  fact,  present  in  less  num- 
bers when  the  latter  process  is  going  on.  Let  us  consider  the 
relations  of  these  branched  cells  to  the  lymphatics.  The  larger 
blood-vessels  are  usually  accompanied  by  a  lymphatic  on  each 
side,  which  gives  off  branches  at  irregular  intervals,  finally 
breaking  up  into  a  capillary  plexus,  which  may  ensheath  the 
accompanying  blood-vessels,  or  even  enclose  a  blood-capillary 
plexus.  When  the  latter  exists  in  a  perilymphangeal  nodule, 
the  lymphatic  capillary  may  apparently  communicate  directly 
with  the  lacunsD  and  canaliculi,  the  endothelial  cells  compos- 
ing the  capillary  being  continuous  with  those  which  invest  the 
spaces,  and  covering  externally,  it  may  be,  the  blood-capillary 
as  well  (Klein,  Delaiield). 

Course  and  termination  of  the  lymphatic  radicles. — In 
tracing  the  lymphatic  capillaries  we  find  that  they  run  in  every 
direction,  branching  irregularly,  and  vary  in  calibre  and  num- 
ber in  different  parts.  It  is  very  difficult  to  trace  one  of  them 
to  a  positive  termination.  The  interstices  of  the  connective- 
tissue  fasciculi  in  brushed  silver  preparations  sometimes  pre- 
sent an  irregular  shape,  as  if  they  were  enclosed  by  irregular 
cells.  This  appears  to  me  to  be  often  due  to  the  convolutions 
of  the  fasciculi,  made  more  irregular,  perhaps,  by  a  cement 
substance,  or  an  interfascicular  substance,  either  fluid  or  semi- 
fluid, which  has  been  coagulated  by  the  processes  following 
death,  and  by  the  action  of  our  reagents.  The  irregular  action 


THE    LYMPHATIC    SYSTEM.  169 

of  silver,  which  produces  so  many  doubtful  pictures,  may  aid 
in  producing  this  appearance.  The  extreme  mobility  necessary 
in  some  forms  of  connective  tissue  demauds  extreme  flexibility 
as  a  quality  of  its  elements,  thus  facilitating  great  variation  in 
structural  arrangement  under  different  conditions. 

Artificial  injection  of  the  lymphatics.  —  If  we  inject  this 
tissue,  by  puncture  with  a  hypodermic  syringe,  we  can  fill  the 
lymphatic  vessels  and 
also  the  interstices,  so 
that  they  are  continu- 
ous ;  but  the  question 
whether  this  is  a  natur- 
al or  an  artificial  trans- 
ition is  one  about  which 
histologists  still  differ. 
Theoretically,  we  may 
consider  that  such  com- 
munications exist  to 


extent,      at      least  FIG.  75.—  From  mesentery  of  cat:  silver-stained  right  por- 

.  tion  denuded  of  endothelium,  showing,  A.  branched  cells,  with 

great]  V    increased  B<  intervening  spaces  ;  left  portion,  endothelial  layer  preserved  ; 

•*  C,  pseucio-stornata  ;  D,  nuclei  ;  E,  elastic  fibres. 

vascular  tension    takes 

place.    But,  at  the  same  time,  many,  or  even  most  of  the  in- 

terstices may  be  closed  spaces. 

It  is  not  a  matter  of  great  consequence,  physiologically  speak- 
ing, since  not  only  fluids  but  lymphoid  corpuscles  can  penetrate 
partitions  which  fail  to  resist  so  slight  an  injecting  force  as  is 
sufficient  to  unite  these  spaces  and  the  lymphatic  capillaries.1 
The  fact  that  injections  can  be  made  without  forming  a  com- 
munication (Frey)  does  not  prove  that  the  latter  does  not 
exist  ;  it  may  be  due  to  an  imperfect  injection.  As  we  shall 
see  later,  the  wandering  propensities  of  the  lymphoid  cor- 
puscles would  almost  exclude  the  possibility  of  the  connective- 
tissue  interstices  remaining  closed  spaces  everywhere. 

Endothelium  and  stomata.  —  We  have  already  referred  to 


1  Thoma  and  Arnold  have  shown  that  injections  into  the  veins,  in  a  living  animal, 
of  insoluble  coloring  matters  (not  distending  the  vessels,  however),  pass  between  the 
endothelial  cells  and  find  their  way  into  the  clefts  and  channels  of  the  deeper  tissues. 
The  possibility  of  absorption  taking  place  through  the  intercellular  substance  which, 
after  all,  may  only  be  a  semifluid  material  filling  a  space  which  varies  in  size  under 
different  conditions,  throws  light  on  many  of  the  difficult  problems  of  absorption, 
secretion,  and  excretion,  and  numerous  pathological  processes. 


170  MANUAL    OF   HISTOLOGY. 

Recklinghausen' s  observation,  that  communication  exists  be- 
tween the  abdominal  and  pleural  cavities  by  means  of  small 
openings  in  the  central  tendon  of  the  diaphragm.  By  injecting 
some  insoluble  coloring  matter,  held  by  fluid  in  suspension, 
into  the  abdominal  cavity,  he  obtained  a  fine  injection  of  the 
lymphatics  of  the  central  tendon,  and  was  able  to  detect  the 
substance  on  its  pleural  surface.  The  experiment  may  be  re- 
versed by  injecting  the  pleural  cavity.  He  was  able  to  see  the 
actual  passage  of  milk-globules  into  these  openings  by  remov- 
ing a  portion  of  the  fresh  tendon  upon  a  cork  ring,  its  pleural 
surface  upward,  placing  a  drop  of  milk  upon  it,  and  observing 
with  the  microscope  the  nearly  round  openings,  large  enough 
to  admit  at  once  two  or  three  of  the  milk-globules  which  ran 
toward  these  openings  in  little  eddies,  and  disappeared  below. 
He  stained  this  membrane  with  nitrate  of  silver,  and  found 
that  the  openings  corresponded  to  perforations  between  the 
endothelial  cells  leading  perpendicularly  or  obliquely  to  the 
lymphatics.  Schweigger-Seidel  and  Doigiel  observed  similar 
openings  leading  from  the  abdominal  cavity,  through  the  retro- 
peritoneal  membrane,  into  the  cysternce  lymphaticce  magna  of 
the  frog.  Dybkowsky  showed  that  colored  fluids  placed  in  the 
pleural  cavity  were  absorbed  by  the  lymphatics  of  the  inter- 
costal pleura.  Schweigger-Seidel,  Doigiel,  and  Ludwig  con- 
firmed the  observations  of  Recklinghausen  in  connection  with 
the  central  tendon  of  the  diaphragm,  and  it  is  now  generally 
admitted  that  such  openings  exist,  not  always  freely  open, 
however,  but  sometimes  with  a  valve-like  cleft.  It  must  not 
be  understood  that  the  small  bead-like  spots  and  the  dark 
spots  between  the  cells  are  true  stomata.  It  is  not  definitely 
known,  in  fact,  what  they  really  represent.  Oedmannson  first 
described  them,  not  only  on  the  serous  membranes,  but  also 
on  the  endothelial  layer  of  the  chyle- vessels.  They  are  very 
numerous  directly  over  the  lymph-vessels  of  the  central  tendon 
on  its  peritoneal  surface  (Dybkowsky). 

Ranmer^s  mews  on  false  stomata. — Ranvier  has  an  in- 
geneous  theory  explaining  the  formation  of  these  objects, 
which  have  been  termed  false  stomata^  also  of  the  true  sto- 
mata and  the  fenestra  of  the  omen  turn.  He  considers  that  the 
lymphoid  corpuscles,  which  are  always  to  be  found  in  serous 
cavities,  penetrate  the  membrane,  making  a  depression  or  per- 
foration, sometimes  remaining,  sometimes  escaping  again.  In 


THE    LYMPHATIC    SYSTEM.  171 

the  majority  of  cases  the  black  spots  are  formed  by  the  albu- 
minous serum  which  these  openings  retain  by  capillary  attrac- 
tion, having  been  coagulated  and  stained  by  the  nitrate  of 
silver,  producing  a  plug.  In  other  cases,  a  globular  cell  re- 
sembling a  lymphoid  corpuscle  occupies  the  stoma,  surrounded 
by  a  black  margin  due  to  the  action  of  the  silver.  Other  cells 
have  a  greater  resemblance  to  small  endothelial  cells  than  to 
lymphoid  corpuscles.  The  irregularity  of  their  distribution  in 
different  membranes,  in  different  animals,  and  at  different 
ages,  seems  to  favor  the  idea  of  such  an  accidental  manner  of 
formation. 

Klein  on  true  and  false  stomata. — Klein  divides  the  sto- 
mata  vera,  or  true  stomata,  into  two  classes  :  a,  those  which 
form  the  mouth  of  a  vertical  lymphatic  channel  leading  to  a 
superficial  vessel  (they  have  a 
special  endothelial  lining) ;  and 
&,  those  formed  by  discontinuity 
between  the  endothelium  of  the 
surface  leading  into  a  simple 
lymphatic  sinus  near  the  sur- 
face, and  lined  only  on  the  lower 
surface  with  endothelium.  Pseu- 
do-stomata,  or  false  stomata,  may 
be  produced,  according  to  this 
observer,  by  the  prolongations  of 
the  sub- endothelial  branched  cells 

-,  /.  ,  ,.  FIG.  76.— Frond  of  fern  (Osmtmda  Clayto- 

beCOimng    free    by  projection    OUt-       niana),  under-surface  showing  stomata. 

ward    between    the    endothelial 

cells.  In  pathological  conditions  he  has  seen  an  extensive 
cell-proliferation  going  on  from  one  of  these  projecting  pseudo- 
stomata.  Ranvier  accounts  for  the  origin  of  the  fenestra 
of  the  omentum  in  a  similar  manner,  as  for  the  stomata.  It 
is  of  interest  to  know  that  the  openings  do  not  exist  before 
birth,  but  increase  in  size  and  number  as  age  advances. 
Klein,  on  the  other  hand,  considers  that  the  openings  in  the 
omentum  are  produced  by  a  process  of  vacuolation.  The 
arrangement  of  the  connective-tissue  fasciculi  around  these 
openings  is  not  that  of  complete  rings,  but  is  such  that  each 
opening  is  bordered  by  several  fibres  which  take  part  in  the 
formation  of  other  openings  in  consequence  of  the  irregularity 
in  their  arrangement.  The  endothelial  cells  may  form  a  com- 


172  MANUAL    OF    HISTOLOGY. 

plete  tube  in  some  of  the  narrow  trabeculse,  in  which  a  sin- 
gle cell  may  complete  the  circumference.  Klein  states  that 
when  these  openings  take  place,  the  connective-tissue  cells  pre- 
viously situated  between  the  connective- tissue  bundles,  come 
to  lie  on  the  lateral  surface  which  is  now  free.  This,  he 
thinks,  establishes  the  fact  that  the  latter  may  be  converted 
into  true  endothelial  cells.  Delafield,  in  considering  the  ques- 
tion of  the  re-formation  of  the  endothelium  on  serous  mem- 
branes, after  hydrothorax,  remarks  that  it  would  seem  to  be 
reproduced  from  the  old  endothelium,  or  from  migrating  white 


FIG.  77. — From  silver-stained  omentum  of  cat:  A,  fenestra;  B,  intercellular  1  ines  of  upper  surface; 
C,  nuclei  of  same  :  D,  intercellular  lines  of  lower  surface ;  E,  nuclei  of  same  ;  F,  nuclei  in  wall  of  opening  ; 
corresponding  cell-forms,  part  of  upper  and  pan  of  lower  surface. 

blood-cells,  or  from  sub-endothelial  connective-tissue  cells, 
although  he  has  not  seen  sufficient  proof  to  establish  any  oi: 
these  theories. 

The  nerves  of  tJie  peritoneum  have  been  studied  by  Cyon. 
They  enter  the  mesentery  with  the  blood-vessels  as  fasciculi  of 
medulla  ted  nerve-fibres,  and,  dividing  laterally,  lose  their  med- 
ullary sheath  and  form  a  plexus,  the  fibres  of  which  show 
projecting  nuclei  at  various  points.  The  walls  of  the  arteries 
receive  a  rich  supply  of  these  fibres.  A  lymph-space,  surround- 
ing the  fibres,  can  sometimes  be  demonstrated. 

Intimate  structure  of  lymphatic  vessels. — A  lymphatic  ves- 
sel may  be  considered  as  a  serous  membrane  with  only  one  free 
surface,  rolled  in  the  form  of  a  tube,  its  endothelial  layer  form- 
ing the  intima,  resting  upon  an  elastic  reticulum,  and  an  ad- 
ventitia  or  external  envelope  of  connective-tissue  fasciculi,  as 
in  the  serous  membranes.  In  the  finest  capillaries  only  the  en- 
dothelial layer  is  independent,  although  they  lie  surrounded 


THE    LYMPHATIC    SYSTEM. 


173 


by  elastic  fibres  and  connective-tissue  fasciculi.  In  the  larger 
trunks,  smooth  muscular  elements  form  a  middle  layer.  The 
endothelial  cells  of  the  lymphatics  have  a  more  sinuous  outline 
than  the  spindle-shaped  cells  of  the  blood-capillaries  ;  they  are 
often  irregularly  dentated  like  the  cranial  sutures.  The  calibre 
of  the  lymphatics  is  also  much  more  irregular  than  that  of 
blood-vessels.  As  they  increase  in  size,  the  tissues  external  to 
the  endothelium  assume  more  and  more  the  character  of  ves- 


Fio.  78. — Central  tendon  of  the  rabbit,  treated  with  solution  of  nitrate  of  silver,  the  most  superficial 
serous  layer  immediately  adjoining  the  pericardium  being  shown  :  a,  lymphatic  capillaries  ;  ft,  their  ori- 
gin ;  c,  serous  canals  with  communications ;  d,  serous  canals  equal  in  width  to  the  origin  of  the  lympha- 
tic vessels ;  et  blood-vessel  with  epithelial  cells.  Magnified  300  diameters.  Recklinghausen. 

sels  with  independent  walls  ;  they  finally  resemble  the  veins 
in  the  largest  trunks,  except  that  they  possess  more  muscular 
tissue  than  the  latter. 

The  diameter  of  the  lymphatic  capillaries  is  very  variable  ; 
they  are  generally  larger  than  the  blood-capillaries,  ranging 
from  0.013—0.045  mm.  (Frey).  Branches  of  0.2256— .2609  mm. 
may  possess  three  layers  (Kolliker).  The  vessels  are  richly 
supplied  with  valves,  which  are  formed  from  the  intima. 

Variations  in  shape. — Here  let  us  consider  an  important 
characteristic  of  the  lymphatic  system,  viz.,  its  irregularity. 


174  MANUAL    OF    1IISTOLOGY. 

In  this  respect  it  contrasts  very  decidedly  with  the  blood-vas- 
cular system.  In  the  calibre  of  its  vessels  in  different  regions, 
in  different  parts  of  the  same  organ,  and  even  in  different  parts 
of  the  same  vessel,  it  is  extremely  irregular.  A  vessel  of  small 
calibre  may  suddenly  expand  into  a  saccular  shape,  which 
may  have  its  diverticula  or  branches,  or  may  form  a  chain  of 
lacunae.  It  is  true  that  these  dilatations  are  formed  just  in 
front  and  behind  the  valves  quite  regularly,  but  they  are  also 
found  everywhere,  being,  in  fact,  a  characteristic  of  these  ves- 
sels. 

Topographical  peculiarities. — Nor  is  a  uniform  direction  to 
be  observed  in  the  distribution  of  these  vessels,  for  while  they 
usually  accompany  arteries,  lying  outside  the  accompanying 
veins,  they  frequently  take  strange  courses.  A  lymphatic  may 
suddenly  leave  its  companions  to  strike  across  a  comparatively 
non-vascular  field  of  tissue  to  share  its  fortunes  with  another 
set  of  blood-vessels.  Respecting  the  capillary  lymphatics, 
their  place  seems  to  be  the  middle  ground  between  the  blood- 
capillaries,  just  where  we  would  expect  to  find  this  drainage 
system.1  They  lie  deeper  in  the  skin  and  mucous  membrane 
than  the  blood-vessels  (Recklinghausen).  The  dispute  con- 
cerning the  question  as  to  whether  the  smaller  lymphatics 
have  a  distinct  wall  or  are  simple  spaces,  probably  has  been 
largely  due  to  the  variation  in  the  structure  of  the  lymphatics 
in  the  same  tissue  or  organ  in  different  animals,  or  in  the  same 
animal  at  different  ages. 

The  thoracic  duct,  which  represents  the  other  extreme  in 
the  structure  of  lymphatic  passages,  has  an  endothelial  layer 
supported  by  a  reticulum  of  elastic  fibres,  which  mingles  with 
the  next  layer,  consisting  of  smooth  muscular  elements  run- 
ning in  every  direction,  the  transverse  elements  predominating. 
The  adventitia  of  connective- tissue  fasciculi  and  elastic  fibres 
completes  its  coats.  The  muscular  layer  in  man  is  highly  de- 
veloped compared  with  quadrupeds  (Ranvier). 


1  On  the  external  ear  of  a  rat  whose  blood-vessels  are  injected  with  colored  gela- 
tine, and  whose  lymphatic  vessels  are  rendered  visible  by  silver,  the  larger  centrifu- 
gal lymph-vessels  are  seen,  even  with  low  powers,  to  be  surrounded  by  a  network  of 
blood-capillaries.  The  same  has  been  demonstrated  in  the  mesentery,  the  dia- 
phragm, and  the  posterior  extremities. — Ueber  ein  die  Lymphgefasse  um-spinneudes 
Netz  von  Blutcapillaren,  von  Alex.  Dogiel.  Arch.  f.  mikroskop.-  Anat.  Bd.  17.  3. 
Heft,  S.  335-340. 


THE    LYMPHATIC    SYSTEM.  175 

TJie  subarachnoid  and  subdural  lymph-spaces  and  their 
prolongations. — Axel  Key  and  Retzius  have  shown  that  be- 
sides the  great  subarachnoid  a"nd  subdural  lymph-spaces  of 
the  brain  and  spinal  cord,  connecting  with  them  are  spaces  en- 
closing the  nerve-fibres  of  the  cord,  and,  what  is  still  more 
remarkable,  extending  outward  on  the  peripheral  nerves.  The 
nerves  of  special  sense,  the  olfactory,  the  optic,  and  the  audi- 
tory, form  no  exception  to  this  rule.  Even  the  ganglia  of  the 
sj^mpathetic  system  and  their  fibres  have  similar  spaces,  which 
are  in  connection  with  the  cord.  Nor  is  this  the  end  of  the 
intricate  labyrinth.  Each  nerve-fibre  has  a  space  immediately 
outside  of  the  sheath  of  Schwann,  between  the  latter  and  the 
so-called  fibrillary  sheath,  through  which  it  communicates  with 
the  perineural  sheath-space,  and  through  the  latter  with  the 
lymph-spaces  of  the  central  nervous  system.  That  they  are 
true  lymphatic  spaces  is  shown  by  the  fact  that  they  are  lined 
by  a  layer  of  endothelial  cells.  Obersteiner  demonstrated  by 
injections  that  the  nerve-cells  also  possess  pericellular  spaces 
connected  with  those  of  the  corresponding  fibres,  a  fact  which 
I  can  corroborate.  Key  and  Retzius  say  that  this  whole  lym- 
phatic system  is  nowhere  in  direct  communication  with  the 
ordinary  lymphatic  system,  and  that  they  have  never  seen  the 
latter  injected  through  the  former,  except  when  extravasation 
occurred.  Bogras  was  the  first  (1825)  to  inject  the  nerves.  He 
used  quicksilver,  and  succeeded  in  injecting  the  peripheral 
nerves  up  to  the  ganglia,  and  made  injections  from  the  dura 
down  to  the  ganglia.  He  failed  with  the  olfactory,  optic,  and 
acoustic.  Cruveilhier,  and  later,  Robin,  confirmed  the  fact 
that  such  injections  are  possible.  Robin,  in  1858,  and  after- 
ward, His,  in  1863,  demonstrated  the  perivascular  lymph- 
spaces  of  the  central  nervous  system. 

Lymphatics  of  tendons. — Axel  Key  and  Retzius,  and  also 
Hertzog,  have  shown  that  the  tendons  possess  spaces  which 
may  be  injected.  From  the  spaces  formed  by  the  endotenium 
and  the  peritenium,  which  communicate,  connections  exist 
with  the  deep  and  superficial  lymphatics  of  the  tendon. 

The  development  of  the  lymphatics  is  by  a  process  of  bud- 
ding and  vacuolation  similar  to  that  which  takes  place  in  the 
blood-vessels. 

Lymphatic  glands. — We  now  pass  to  the  consideration  of 
the  lymphatic  bodies  called  glands,  ganglia,  or  nodes.  Their 


176  MANUAL    OF    HISTOLOGY. 

distribution  does  not  concern  us  here ;  it  is  sufficient  to  say 
that  they  are  very  variable  in  size  and  number  in  different 
regions,  being  supplied  to  nearly  all  the  lymphatic  trunks, 
with  which  they  are  connected  by  the  so-called  afferent  and 
efferent  branches.  The  former  usually  consist  of  several  small 
branches  ;  the  latter  generally  enter  as  single  large  trunks. 

The  shape  of  the  lymph-nodes  may  be  spherical,  oval,  ob- 
long, or  reniform.  In  the  latter,  which  is  by  far  the  most  fre- 
quent form,  the  afferent  vessels  penetrate  the  capsule  on  the 
convex  surface,  while  the  efferent  branch  escapes  at  the  hilus. 
In  the  other  forms  it  is  difficult  to  determine  which  are  the 
afferent  and  which  the  efferent  vessels.  A  lymph-node  con- 
sists essentially  of  spheroidal  and  cylindrical  masses  of  reticular 
tissue,  containing  lymphoid  corpuscles,  richly  supplied  by  a 
blood- capillary  system,  and  sustained  in  place  by  a  framework 
of  connective  tissue,  with  elastic  and  sometimes  muscular  ele- 
ments, forming  a  network  around  the  masses  for  the  circula- 
tion of  lymph,  and  expanding  externally  to  form  a  capsule. 
The  gland  is  usually  divided  by  histologists  into  a  cortical  and 
a  medullary  portion,  the  former  being  simply  that  part  in  which 
the  lymphoid  masses  assume  a  spheroidal  form  (the  follicles), 
this  being  the  more  peripheral  portion  of  the  node,  or  the  part 
farthest  from  the  hilus,  when  that  exists.  The  medullary  sub- 
division represents  the  remaining  portion,  and  its  lymphoid 
material  is  in  the  form  of  cylindrical  or  cord-like  prolongations 
from  the  follicles.  The  capsule  is  composed  of  connective  tis- 
sue, the  fibres  of  which  run  in  different  directions  in  its  exter- 
nal layers,  possessing  elastic  fibres,  flat  cells,  and  a  slight 
amount  of  fat-tissue.  The  lymphatics  of  the  capsule  are  found 
mostly  in  its  outer  layers.  The  inner  layers  present  a  more 
stratified  appearance  on  account  of  the  regularity  of  their 
bundles  and  the  interposed  connective-tissue  cells.  An  elastic 
network  and  smooth  muscular  elements  are  found  here,  and 
rilso  in  the  septa,  and  are  developed  in  some  animals  to  a  high 
degrees  It  is  from  the  inner  layers  of  the  capsule  that  the 
septa  are  given  off  to  form  the  framework  of  the  node.  These 
consist  primarily  of  trabeculse,  which,  passing  between  the  fol- 
licles, converge  toward  the  medullary  portion,  where  they  inter- 
lace with  the  lymphoid  cords  of  the  latter,  and  may  again  unite 
at  the  hilus  (stroma  of  His).  They  have  a  structure  similar  to 
that  found  in  the  portion  of  the  capsule  from  which  they  have 


THE    LYMPHATIC    SYSTEM. 


177 


their  origin.  These  septa  are  not  complete  partitions,  but  consti- 
tute an  open  framework,  which,  in  consequence  of  its  radiating 
arrangement,  produces  wider  spaces  in  the  cortical  than  in  the 
medullary  portion.  To  this  the  follicles  correspond  by  being 
broadest  at  their  peripheral  portions.  It  must  not  be  under- 
stood that  the  lymphoid  masses,  either  follicular  or  cylindri- 
cal, are  closely  embraced  by  the  septa  ;  they  are  separated  from 
the  latter,  and  from  the  sheath  as  well,  by  spaces,  the  "  invest- 
ing spaces  of the  follicular  portion"  (Frey),  or  sinuses  of  tlie 


FIG.  79. — Section  of  the  medullary  substance  of  a  lymphatic  gland  from  the  ox :  a,  follicular  cord  ;  ft, 
trabeculae ;  c,  path  pursued  by  the  lymph  ;  d,  blood-vessels.    Magnified  300  diameters.    Recklinghausen. 

cortical  substance  (Ranvier),  and  the  lymph-passages  (Frey) 
or  cavernous  plexus  (Ranvier)  of  the  medullary  portion.  These 
spaces  are  maintained  by  a  network  of  line  fibres  (tenter-fibres 
of  Frey)  derived  from  the  septa,  being  given  off  at  nearly  right 
angles  to  the  latter.  The  bundles  of  fibres  composing  them 
divide  and  reunite,  forming  meshes,  and  extend  to  the  follicles 
and  cords.  In  reality,  they  do  not  end  here,  but  are  continued 
to  form  the  reticular  tissue  of  these  bodies  by  dividing  into  a 
still  finer  network,  which  differs  in  the  different  portions  only 


178  MANUAL    OF    HISTOLOGY. 

by  slight  variations  in  the  size  of  the  meshes  and  the  fineness  of 
the  fibres,  the  meshes  being  longer  and  narrower  in  the  peri- 
pheral portions  of  the  follicles  and  in  the  cords  than  in  the 
central  part  of  the  former.  This  sort  of  tissue  has  received 
different  names :  cytogenous  tissue  (Kolliker),  adenoid  tissue 
(His),  reticular  tissue  (Frey,  Ranvier).  It  is,  as  the  latter  name 
implies,  a  network,  the  fibres  of  which  run  in  every  direction, 
being  applied  to  one  another  in  the  same  manner  as  .the  fibres 
of  the  omentum  already  described.  The  nuclei,  which  are 
more  oval  and  larger  than  the  lymphoid  corpuscles,  appear  at 
the  junction  of  fibres,  simply  rest  upon  them,  and  can  be  re- 
moved by  brushing.  They  are  endothelial  cells,  and  in  silver- 
stained  preparations  an  endothelial  layer  can  be  seen  to  cover 
the  septa,  the  reticulum  of  the  lymph-passages,  and  the  folli- 
cles in  the  same  manner  that  the  fine  bundles  of  the  omentum 
are  covered  ;  that  is,  the  spaces  between  the  bundles  are  no- 
where covered,  but  each  bundle  is  wrapped  by  these  cells. 
This  can  only  be  seen  after  the  lymphoid  corpuscles  that  occupy 
the  meshes  have  been  removed  by  brushing.  The  endothelial 
layer  is  continuous  with  that  of  the  afferent  and  efferent  lym- 
phatic vessels,  which  communicate  with  the  lymph-spaces  of 
the  node,  as  shown  by  injections. 

According  to  Klein,  the  clinical  nature  of  reticular  tissue 
does  not  correspond  to  connective  tissue  proper  or  to  elastic 
tissue.  Filling  the  meshes  of  the  follicular  and  cylindrical 
portions  of  the  lymphoid  masses  are  the  lymphoid  corpuscles, 
two  or  more  in  each  mesh.  Lymphoid  corpuscles  are  also 
found  in  the  investing  or  lymph-spaces,  but  they  are  easily 
brushed  out,  while  a  much  longer  brushing  is  required  to  de- 
tach them  from  the  other  portions.  The  corpuscles  are  some- 
what larger  than  the  colorless  blood-corpuscles,  though  vari- 
able in  size.  They  possess  a  single  prominent  nucleus,  -which 
is  readily  stained  by  most  coloring  matters.  The  amount  of 
protoplasm  they  possess  is  small.  When  examined  in  a  moist 
chamber  at  a  temperature  of  36°  to  37°  C.,  some  of  them  ex- 
hibit amoeboid  movements,  the  small  ones  having  the  least 
protoplasm  around  their  nuclei  being  most  active  (Ranvier). 
Klein  states  that  corpuscles  are  to  be  found  which  are  larger 
than  the  others,  having  more  protoplasm,  and  often  two  nuclei. 
He  considers  them  in  a  more  advanced  stage  of  development 
than  the  others. 


THE    LYMPHATIC    SYSTEM.  179 

The  arteries  and  veins  of  the  lymphatic  nodes  have  their 
chief  entrance  at  the  hilus,  with  the  efferent  lymphatic  vessels. 
The  main  trunks  divide  to  pass  into  the  septa.  Still  finer 
divisions  pass  into  the  reticular  tissue,  forming  a  rich  capillary 
network  in  the  follicles  and  cylinders,  most  marked  at  the  sur- 
face of  these  bodies.  In  the  cylinders  a  single  axial  arterial 
branch,  surrounded  by  a  peripheral  capillary  system,  may  fur- 
nish the  supply.  Another  source  of  blood-supply  may  be  from 
the  capsule  ;  small  branches,  both  arterial  and  venous,  which 
ramify  in  its  layers,  send  finer  branches  inward,  encircling  the 
follicles  and  traversing  the  septa  and  reticulum  of  the  lymph- 
spaces.  The  capillaries  possess,  besides  their  proper  wall,  a 
sheath  derived  from  the  reticulum. 

Nerves  of  the  lymphatic  nodes. — Little  is  known  on  this 
point.  Nerve-fibres  enter  with  the  blood-vessels  in  some  of 
the  larger  glands  of  man  (Kolliker),  and  non-medullated  nerve- 
fibres  have  been  seen  in  the  lymphatic  nodes  of  the  ox.  Con- 
cerning the  lymphatics,  they  exist,  as  we  have  seen,  in  the 
outer  layers  of  the  capsule,  and  do  not  differ  from  those  in 
other  regions,  forming  a  network  in  the  capsule.  They  are 
continuous  externally  with  the  afferent  lymphatics,  and  inter- 
nally with  the  lymph-spaces  already  described. 

The  numerous  lymphoid  organs  are  all  constructed  upon  a 
plan  similar  to  that  of  the  nodes,  in  that  they  all  represent 
modifications  in  the  arrangement  of  reticular  tissue  and  its 
vascular  supply. 

Injection  of  a  lymphatic  gland. — We  may  obtain  an  injec- 
tion of  the  lymph-passages  in  the  node  by  puncturing  the 
capsule  with  an  ordinary  hypodermic  syringe  (a  method  for 
which  we  are  indebted  to  Hyrtl),  and  injecting  a  mixture  of 
Prussian  blue  and  gelatine  (soluble  blue,  25,  solid  gelatine,  1). 
It  is  best  to  inject  one  of  a  series  of  connected  nodes,  in  place, 
exposing  them  by  dissection  in  a  freshly  killed  animal.  One 
gland  is  then  injected  from  the  other  through  the  afferent  and 
efferent  vessels  (Ranvier).  They  are  excised  and  hardened  in 
Miiller's  fluid  or  alcohol ;  sections  are  then  made  with  a  micro- 
tome, after  which  they  may  be  washed  in  water,  stained  for  a 
few  minutes  in  picro-carminate  of  ammonia  (1  per  cent.),  again 
washed,  and  then  mounted  in  glycerine  or  Canada  balsam. 

Method  of  studying  the  gland  substance. — For  the  purpose 
of  demonstrating  the  reticulum  of  the  lymph-spaces  and  the 


180  MANUAL    OF    HISTOLOGY. 

lymphoid  masses,  the  node  must  be  hardened  in  alcohol,  bi- 
chromate of  potassa,  or  (Ranvier's  method)  placed  for  twenty- 
four  hours  in  a  concentrated  solution  of  picric  acid  ;  sections 
are  then  to  be  made,  after  which  they  are  gently  brushed  and 
agitated  in  water  with  a  camel'  s-hair  brush  to  disengage  the 
lymphoid  corpuscles  (we  are  indebted  to  His  for  the  method  of 
brushing).  After  staining,  preferably  with  hematoxylin,  which 
exhibits,  in  a  beautiful  manner,  the  lymphoid  corpuscles  and 
the  darker  nuclei  of  the  endothelial  layer,  they  may  be 
mounted  in  the  usual  manner. 

Returner's  plan. — The  plan  particularly  recommended  by 
Ranvier  is  as  follows  :  the  node  remains  for  twenty -four  hours 
in  a  mixture  of  alcohol  (36°  Cartier),  one  part,  water,  two 
parts  ;  then  for  twenty-four  hours  in  a  syrupy  solution  of  gum- 
arabic,  and  is  afterward  hardened  in  alcohol  sufficiently  for 
section  cutting  in  a  microtome.  Floating  them  in  a  shallow, 
flat  dish,  in  water  two  or  three  centimetres  deep,  the  gum  is 
dissolved,  and  the  brush  used  in  a  very  delicate  manner  ;  the 
sections  may  then  be  stained  and  mounted,  as  described  above. 
The  degree  of  hardness,  and  the  force  and  duration  of  the  brush- 
ing process,  will  determine  the  result,  which  practice  only  will 
make  perfect.  The  lymphoid  corpuscles  in  the  lymph-passages, 
that  is  to  say,  in  the  parts  which  fill  with  the  blue  injection 
fluid,  as  previously  described,  are  first  removed,  and  additional 
brushing,  when  the  proper  degree  of  hardening  has  been  at- 
tained, will  enable  one  to  remove  these  bodies  from  the  folli- 
cles and  cords,  and  also  to  remove  the  endothelial  cells  which 
rest  upon  the  fibres  of  the  reticulum  and  septa. 

Other  methods  of  injecting  glands. — A  node  removed  imme- 
diately after  death  and  injected  by  puncture  with  a  1  per  cent, 
solution  of  hyperosmic  acid,  then  placed  in  water  for  one  or 
two  hours,  and  afterward  hardened  in  alcohol,  cut  in  sections, 
colored  by  picrocarminate  of  ammonia,  and  mounted,  gives 
good  results. 

The  best  method  for  showing  the  endothelial  layer  is  by 
interstitial  injection  (puncture)  with  a  solution  of  nitrate  of 
silver,  1 — 300  ;  harden  afterward  by  freezing,  and  make  sec- 
tions. 

Before  closing  this  chapter,  let  us  take  a  retrospective  vie\v 
of  our  subject.  In  doing  so,  it  is  almost  impossible  to  avoid 
associating  the  connective- tissue  cell  with  other  forms  which 


THE   LYMPHATIC    SYSTEM.  181 

seem  to  be  its  antecedents,  modifications,  or  derivatives,  viz., 
the  extensive  system  of  branched  corpuscles  in  the  matrix  of 
the  serous  membranes,  whose  growth  and  proliferation  form 
large  tracts  when  they  possess  a  sufficient  blood-supply,  and 
between  which  the  lymph  circulates,  affording  a  channel  of 
escape  for  the  dischajged  bits  of  protoplasm,  their  offspring  ; 
the  throwing  off  of  similar  bits  of  protoplasm  by  the  surface 
endothelium  of  the  serous  membranes ;  the  probable  transfor- 
mation of  the  branched  cells  into  fat-cells,  and  the  conversion  of  a 
branched  connective- tissue  cell  into  an  endothelial  cell,  when  it 
reaches  a  free  surface.  Again,  the  fact  that  similar  endothelial 
cells  line  the  blood  and  lymph  channels,  and  also  cover  the  reti- 
culum  of  the  lymphatic  nodes  and  follicles,  and  that  in  the 
latter  forms,  when  we  have  also  a  rich  capillary  blood-supply — 
that  is,  a  supply  of  oxygen — the  accumulation  and  probable 
elaboration,  if  not  proliferation,  of  lymphoid  corpuscles  goes  on 
in  a  more  extensive  manner  than  in  the  lyrnphangeal  tracts  ; 
taken  together,  all  point  to  the  idea  that  they  are  different 
forms  of  protoplasm  which  have  been  converted,  or  are  con- 
vertible, one  into  the  other  under  proper  conditions  of  tempera- 
ture, food-supply,  and  excitability,  the  definite  limitations  of 
which  are  but  imperfectly  known. 

In  the  germinating  tracts,  superficial  and  deep,  of  the  serous 
membranes,  in  the  lymphatic  nodes  and  follicles  of  the  ali- 
mentary canal,  .and  also  in  the  lymphoid  organs  (spleen,  ton- 
sils, etc.),  we  have  active  farms,  reproduction  by  budding,  and 
division.  The  formation  of  the  lymphoid  corpuscles,  which 
may  be  considered  as  so  many  amoebae  sporting  in  a  nutritious 
fluid,  and  engorging  themselves  with  that  which  is  brought  to 
them  by  the  agency  of  the  absorbents  and  lymph-channels, 
under  conditions  favorable  to  great  activity,  free  to  penetrate 
most  of  the  tissues,  and,  perhaps,  become  fixed  forms.  These 
processes  of  activity,  when  confined  to  the  limits  of  the  organs 
mentioned,  are  conducive  to  life  and  growth,  but  occurring  in 
the  allied  forms  that  have  become  fixed,  as  the  corneal  branched 
cells,  the  connective-tissue  cells,  or  the  endothelial  cells,  to  any 
considerable  extent,  inaugurate  the  processes  of  disease  and 
death.  Thus  these  comparatively  indefinite  and  undifferen- 
tiated  forms  of  protoplasm  may  be  said  to  be  keys  to  life  and 
death. 


182  MANUAL    OF   HISTOLOGY. 


BIBLIOGRAPHY. 

Authors  referred  to  in  the  text : 
BICHAT.     Anat.  gen.     Second  edition.     1812. 
IBID.     Traite  des  membranes.     1816. 
REMAK.     Mailer's  Archiv.     1850. 

BRUCKE.     Ueber  die  Chylusgefasse,  etc.     Sitzb.  der  Wiener  Akad.     1853. 
LEYDIG.     Lehrbuch  d.  Histologie,  etc.     1857. 
VIKCHOW.     Cellular  Pathology.     1860. 
OEDMANNSON.    Virchow's  Archiv.     Bd.  26.     1863. 
CHRZONSZCZEWSKY.     Virchow's  Archiv.     Bd.  31.     1864. 
His.     Archiv  f.  mikrosk.  Anat.     Bd.  I.     1865. 

SCHWEIGGER-SEIDEL  and  DOIGIEL.     Arbeit,  a.  d.  phys.  Lab.  z.  Leipzig.     1866. 
KOLLIKEK.     Handbuch  der  Gewebelehre.     1867. 
CYON.     Arbeit,  a.  d.  Phys.  Anstalt.  in  Leipsig.     1868. 
ROBIN.    Diet.  Ency.  So.  Med.     1870. 

RECKLINGHAUSEN.     The  Lymphatic  System.     Strieker's  Histology.     1872. 
KLEIN.     The  Lymphatic  System.     1873. 
DYBKOWSKY.     Arbeit,  a.  d.  Phys.  Anstalt.  in  Leipsig. 
ARNOLD,  J.     Archiv  f.  path.  Anat.    Bd.  58,  p.  203.     1873. 
THIN.    Proc.  Royal  Soc.     Vol.  22.     1874. 

THOMA.     Centralbl.  f.  d.  med.  Wiss.     1875.    Archiv  f.  path.  Anat.     Bd.  64.     1875. 
KEY,  AXEL,  and  RETZIUS.     Archiv  f.  mikrosk.  Anat.    Bd.  IX.     1875.     (Abstract  of 

large  work  on  the  nervous  system. ) 
HERTZOG.     Zeitschr.  f.  Anat.  und  Entwick.     1875. 
RANVIER.     Traite  technique  d'histologie.     1877  et  seq. 
DELAFIELD.     Path.  Studies.     New  York,  1878—80. 
FREY.     The  Microscope,  etc.    New  York,  1880. 

Among  the  more  recent  authors  that  have  written  on  this  subject  are  : 
HOGGAN.     Proc.  Royal  Soc.     1876—77.     (Two  articles. ) 
LEWIS.     Proc.  Roy.  Society.     1877. 

ROBIN  and  CADI  AT.     Journ.  de  Tanat.  et  de  la  phys.     1876.     No.  6. 
BUDGE.     Arch.  f.  mikrosk.  Anat.     Bd.  X.     1876. 
RIEDEL.     Archiv  f.  mikrosk.  Anat.     Bd.  XI.     1877. 
WITTICH.     Mittheil.  a.  d.  k.  phys.  Lab.     1878. 
MIERZYEWSKI.     Jour,  de  1'anat.  et  de  la  phys.     Paris,  1879. 
RENAUT.     Comptes  rendus  Acad.  des  Sci.     Paris,  1879. 
WEBER-LIEL.     Arch.  f.  path.  Anat.     Bd.  LXXVII.     1879. 
FISCHER.     Arch.  f.  mikr.  Anat.     XVII.     1879-80. 
SITNA.     Wien.  med.  Presse.     XXI.     1879. 


CHAPTER  XIII. 

THE  LIVEE  AND  BILIAEY  APPARATUS. 

BY  DR.  ABRAHAM  MAYER, 

Curator  of  the  Manhattan  Eye  and  Ear  Hospital,  New  York  City. 

THE  liver  is  enclosed  in  a  connective-tissue  capsule,  the 
peritoneum,  which  also  gives  off  secondary  folds,  or  duplica- 
tures,  called  ligaments,  by  which  the  organ  is  held  in  proper 
connection  with  the  adjacent  parts.  The  thickness  of  the  cap- 
sule is  about  0.03  mm.,  and  its  free  surface  is  covered  with  the 
flattened  corpuscles  that  belong  to  serous  membranes  gener- 
ally. This  connective-tissue  covering  is  furthermore  composed 
of  thin  laminae,  which  contain  a  large  number  of  elastic  fibres. 
At  the  transverse  fissure,  where  it  is  continued  into  the  inte- 
rior of  the  organ,  the  same  character  is  maintained.  Here  it 
encircles  vessels,  ducts,  and  nerves,  forming  the  so-called 
Glisson's  capsule,  which,  indeed,  with  its  minute  ramifications, 
traverses  the  whole  interior  of  the  gland.  The  liver  contains, 
in  addition  to  the  glandular  substance,  blood-vessels,  lympha- 
tics, nerves,  and  gland-ducts,  the  whole  held  together  by  the 
framework  of  connective  tissue  just  mentioned,  which  in  the 
human  species  is  but  imperfectly  developed. 

The  hepatic  lobules.— The  glandular  parenchyma  consists 
of  the  so-called  hepatic  lobules,  which  in  the  human  liver  are 
not  completely  separated  from  one  another,  for  the  reason 
just  named.  In  some  of  the  lower  animals,  however,  this  sepa- 
ration is  more  perfect.  In  the  hog's  liver,  for  example,  the 
septa  are  so  well  developed  that  the  lobules  are  plainly  recog- 
nizable by  the  naked  eye. 

To  isolate  the  human  lobules  is  a  matter  of  some  difficulty  ; 
but  it  can  be  accomplished  by  macerating  the  organ  in  water 
from  twelve  to  twenty -four  hours. 

These  lobules  are  also  known  as  the  hepatic  acini,  or  in- 


184 


MANUAL    OF    HISTOLOGY. 


sulce  of  the  liver.  Their  form  is  irregularly  polyhedral,  and 
they  usually  measure  about  4x1  mm.  At  their  bases  they 
are  attached  to  short  twigs  of  the  hepatic  vein,  which  have  a 
thickness  of  from  0.08 — 0.06  mm.,  and  traverse  the  lobules  in 
the  axes  of  their  long  diameters.  As  the  hepatic  vein  ascends 
through  the  lobule,  it  gives  off  innumerable  capillary  branches, 
almost  at  right  angles  to  its  course.  The  latter  pursue  their 
way  to  the  periphery  of  the  lobule,  and  hence  have  a  radial 
direction.  These  capillaries  further  subdivide  within  the  lob- 
ules, and  are  united  to  each  other  by  transverse  branches, 
forming  a  network  with  small  meshes.  At  the  periphery  the 

capillaries  join  the  rami- 
fications of  the  portal 
vein.  The  latter  divides 
within  the  liver  into  nu- 
merous branches,  which 
again  subdivide  at  the 
surfaces  of  the  lobules. 
Their  ultimate  ramifica- 
tions form  the  boundary 
lines  between  adjoining 
hepatic  lobules,  and  it- 
is  for  this  reason  that 
they  have  been  called 
interlobular  veins.1  For 
a  similar  reason  the 
branches  of  the  hepatic  vein,  which  traverse  the  centres  of 
the  lobules,  have  been  called  intralobular '  or  central  veins 2 
(Fig.  80). 

The  interlobular  veins  are  contained  within  interlobular  or 
intermediate  (Hering)  canals  ;  these  are  easily  demonstrable  in 
the  hog's  liver.  In  this  animal  the  adjoining  edges  of  three 
or  four  hepatic  lobules  combine  to  form  a  canal  which  con- 
tains the  interlobular  vessels.  The  latter  are  surrounded  by 
connective  tissue,  which  is  continuous  with  that  of  the  septa 
between  the  lobules.  In  the  human  liver  there  is  a  similar 
arrangement,  but  in  it  the  septa  of  connective  tissue  do  not 
completely  separate  the  lobules,  and,  excepting  at  the  inter- 


PIG.  80. — Injected  liver  of  rabbit,  showing  branches  to 
portal  vein,  capillaries,  and  the  hepatic  veins  in  the  centres  of 
two  lobules.  Frey. 


'Kiernan:  Philosoph.  Trans.,  1833. 

2  Vena3  Centrales,  Krugenberg,  Miiller's  Archiv,  1843. 


THE    LIVER    AND    BILIARY    APPARATUS.  185 

lobular  canals,  the  parenchyma  of  contiguous  lobules  appears 
to  coalesce. 

Nevertheless,  the  substance  of  the  human  liver  can  be  di- 
vided into  distinct  lobules,  and  the  terminal  branches  of  the 
portal  veins  may  be  regarded  as  their  natural  boundaries  (Figs. 
80  and  87).  Starting  with  the  portal  veins,  therefore,  the  course 
of  the  blood  is  as  follows  :  portal  veins,  interlobular  veins,  cap- 
illaries, intralobular  veins,  hepatic  veins,  and  inferior  vena 
cava. 

Sublobular  veins,  according  to  Kiernan,  are  such  branches  of  the  hepatic 
vein  as  are  placed  tinder  the  bases  of  several  lobules,  and  collect  the  blood 
from  their  central  veins. 

The  liver  may  be  injected 'either  through  the  portal  or  he- 
patic veins,  or  through  both.  Good  specimens  may  be  ob- 
tained by  injecting  the  fresh  liver  of  a  dog  or  rabbit  with 
carmine  -  gelatine  through 
the  portal  vein,  then  inject- 
ing fluid  Berlin  blue  into  the 
hepatic  vein,  and  afterward 
hardening  the  organ  in  alco- 
hol. The  central  vein  and 
adjacent  capillaries  will  thus 
be  rilled  with  a  blue  mass, 
while  the  interlobular  and 
portal  veins,  with  the  per- 
ipheral capillaries,  will  con- 
tain the  transparent  red 
mass. 

Tlie  COlor  Of  the   CUt  SUr-  FIG.  81.— Transverse  pection  of  a  human   lobule, 

„  „   ,  ,        ,.  ...  showing  opening  for  central  vein.     Ecker. 

face  of  the  liver  m  its  natu- 
ral condition  is  of  a  uniform  reddish  brown  tint,  and  its  lobular 
structure  is  not  readily  made  out.  Usually,  however,  we  find 
two  shades  or  gradations  in  color ;  one,  corresponding  to  the 
central  veins  of  the  lobules,  is  of  a  dark  red  ;  the  other,  corre- 
sponding to  the  periphery  of  the  lobules,  is  a  lighter  and  yel- 
lowish red. 

Occasionally  these  conditions  are  found  to  be  reversed, 
and  the  difference  of  color  is  due  to  the  fact  that  after  death 
the  central  and  other  hepatic  veins  are  filled  with  blood,  while 
the  portal  and  its  branches  are  empty  ;  and  also  because 


186  MANUAL    OF   HISTOLOGY. 

the  deposit  of  bile-pigment  takes  place  at  the  centres  of  the 
lobules  about  the  intralobular  veins  ;  whereas  a  fatty  infiltra- 
tion, such  as  may  occur  in  normal  livers,  takes  place  at  the 
periphery.  Not  uncommonly  the  yellowish  red  color  at  the 
boundary  of  the  lobules  exists  under  the  form  of  delicate 
markings,  which  are  nothing  more  than  the  empty  interlobular 
branches  of  the  portal  vein. 

Kiernan  occasionally  observed  in  young  subjects  that  the  portal  vein  was 
distended  with  blood,  while  the  hepatic  vein  was  empty.  In  such  cases  the 
periphery  of  the  lobules  was  of  a  darker  color  than  their  centres. 

The  blood-vessels  of  the  liver. — These  have  been  partly  de- 
scribed above.  The  hepatic  artery,  and  duct,  and  portal  vein 
enter  the  liver  at  the  transverse  fissure,  enclosed  within  Glis- 
son's  capsule,  and  continuously  subdivide  as  they  push  their 
way  through  the  parenchyma.  The  subdivisions  of  the  portal 
vein  never  anastomose,  but  are  distributed  around  the  surfaces 
of  the  lobules,  forming  their  boundaries.  At  the  periphery 
they  break  up  into  capillaries  which  enter  the  lobules.  These 
are  about  0.02  mm.  in  diameter,  and  form  a  network,  the 
meshes  of  which  are  scarcely  wider  than  capillaries.  Within  the 
lobule  the  capillaries  unite  to  form  the  central  vein,  and  these 
then  empty  into  branches  of  the  hepatic  vein.  The  subdivi- 
sions of  the  hepatic  vein  are  also  devoid  of  anastomoses,  but 
after  traversing  the  posterior -portion  of  the  liver  in  canals 
(which  they  embrace  closely),  unite  to  form  the  hepatic  vein. 
A  peculiarity  of  this  latter  vein  is  the  fact  that  its  larger 
branches  give  off  successively  small  lateral  twigs,  which  enter 
the  bases  of  the  neighboring  lobules,  so  that  after  dividing 
such  a  branch  lengthwise  it  would  seem  to  be  pierced  by  small 
circular  openings,  which  are  the  orifices  of  the  lateral  branches. 

Not  unfrequently  a  central  (hepatic)  vein  will  divide  into 
two  branches  within  a  lobule,  in  which  case  the  latter  seems 
to  possess  two  apices,  which  become  joined  together  as  we  ap- 
proach its  base.  The  connection  between  the  portal  and  hepatic 
veins  takes  place  only  through,  their  capillaries. 

The  hepatic  artery  is  comparatively  small.  It  enters  the 
liver  together  with  the  duct  and  portal  vein,  and  at  once  breaks 
up  into  branches,  which,  anastomosing  with  each  other,  form  a 
large-meshed  network.  The  arterial  branches  are  distributed 
to  the  vessels  mentioned,  which  they  enclose,  and  also  to  the 


THE    LIVER    AND    BILIARY    APPARATUS.  187 

connective  tissue  which  surrounds  the  latter.  The  hepatic  arte- 
ry also  gives  off  nutrient  branches  which  supply  its  own  walls, 
and  small  twigs,  which,  piercing  the  substance  of  the  liver  be- 
tween the  lobules,  supply  the  branches  of  the  hepatic  vein. 
The  ultimate  branches  of  the  artery  are  contained  within  the 
interlobular  canals,  and  break  up  into  capillaries  at  the  peri- 
phery of  the  lobules,  which  they  traverse  for  a  short  distance 
to  form  a  distinct  network.  There  is  no  communication  between 
the  intralobular  capillaries  of  the  hepatic  artery  and  those  of 
the  portal  vein.  The  former  seem  destined  to  supply  the  ad- 
jacent vessels,  and  probably  the  small  amount  of  intralobular 
connective  tissue  to  be  spoken  of  hereafter. 

It  has  been  thought  by  some  (Chronszewski,  Bindfleisch,  and  others)  that  the 
capillaries  of  the  hepatic  artery  end  midway  between  the  interlobular  and  cen- 
tral veins,  within  the  lobule.  Beale  and  Kiernan  have  noticed  that  an  arterial 
branch  here  and  there  enters  a  lobule ;  while  Theile,  Davis,  and  others  describe 
a  capillary  network  about  the  periphery  of  the  lobules. 

Finally,  branches  of  0.05  to  0.1  mm.  in  diameter  are  dis- 
tributed to  the  capsule  of  the  liver,  where  they  break  up  into 
capillaries,  radiating  in  all  directions  and  anastomosing  with 
each  other  to  form  a  large- meshed  network,  which  communi- 
cates with  the  capillaries  of  the  phrenic,  mammary,  and  supra- 
renal arteries.  This  plexus  empties  into  small  twigs,  the  so- 
called  inner  roots  of  the  portal  vein. 

The  capillaries  of  the  liver  may  be  injected  either  through 
the  hepatic  or  portal  vein,  or  both,  as  before  stated.  For  in- 
jecting the  hepatic  artery  the  author  prefers  his  cold  solution 
of  carmine-glycerine.1  The  gland  to  be  injected  must  be  as 
fresh  as  possible.  If,  for  example,  a  dog  be  selected  for  this 
purpose,  the  abdomen  should  be  opened  and  the  animal  allowed 
to  bleed  to  death  by  section  of  the  vena  cava.  Now  introduce 
into  the  hepatic  artery  the  canula  of  a  syringe  tilled  with  the 
carmine-glycerine,  secure  it  in  place  and  inject.  Harden  the 
organ  in  alcohol,  cut  sections,  and  mount  in  balsam.  The  liver 
will  not  be  uniformly  injected,  and  only  those  portions  can  be 
utilized  in  which  the  injected  mass  seems  to  be  widely  diif  used. 

If,  in  addition  to  the  artery,  the  hepatic  vein  be  injected 
with  a  blue  colored  mass,  beautiful  results  may  be  obtained. 
Sections  in  which  the  lobules  are  cut  transversely  show  the 

1  See  chapter  on  the  Kidney. 


188 


MANUAL    OF    HISTOLOGY. 


central  veins  occupying  the  position  of  the  axes  of  the  lobules 
and  the  capillaries,  pursuing  a  radial  course  and  anastomosing 
with  each  other  by  transverse  communications. 

Since  the  capillaries  successively  divide  from  the  centre 
toward  the  periphery,  it  follows  that  they  are  much  less  numer- 
ous at  the  former  than  at  the  latter  point.  A  section  through 
the  long  axis  of  an  acinus  will  show  that  the  central  vein  is 
divided  lengthwise,  and  that  the  capillaries  are  given  off  from 
it  almost  at  right  angles  to  its  course. 

Nearer  the  summit  of  the  lobule,  however,  the  central  vein 
is  seen  to  break  up  into  diverging  capillaries.  If  the  section 
has  been  made  to  one  side  of  the  central  vein,  but  yet  parallel 
with  its  axis,  many  capillaries  will  be  cut  across,  more  or  less 
transversely,  and  will  then  appear  as  small,  circular,  or  oval 
rings. 

The  connective  tissue  of  the  liver.— Glisson's  capsule  is 
formed  of  longitudinal  bundles  of  connective  tissue  which  are 

loosely  interwoven.  It  serves 
to  bind  together  the  hepatic 
artery,  portal  vein,  and  hepatic 
duct,  and  also  fills  out  the 
small  spaces  left  between  the 
ramifications  of  these  vessels 
(Fig.  82).  Sections  from  a  liver 
hardened  in  chromic  acid  or 
alcohol,  and  immersed  in  a  di- 
lute solution  of  caustic  potassa, 
or  simply  pencilled,  show  the 
connective  tissue  well.  About 
the  hepatic  vein  it  is  thin  and 
dense,  and  firmly  united  to  the  glandular  structure,  so  that 
when  cut  transversely  these  vessels  appear  to  gape.  In  the 
camel  the  connective  tissue  is  greatly  developed,1  even  more  so 
than  in  the  hog.  The  interlobular  septa  are  very  dense  and 
fibrillated ;  in  the  interior  of  the  lobule  the  connective  tissue 
has  a  lamellar  structure. 

According  to  Ewald  and  Kuehne,  minute  bundles  of  fibrous  tissue  extend 
beyond  this  interlobular  connective  tissue,  and  piercing  the  lobules  eventually 
surround  the  central  veins. 


FIG.  82.— Connective  tissue  of  a  child's  "liver, 
after  hardening  in  alcohol  and  pencilling  :  a,  a, 
capillary  vessels  containing  a  few  blood-globules  ; 
6,  ft,  connective-tissue  fibrils ;  c,  c,  liver-cells  not 
removed  by  pencilling. 


1  Turner,  Win.,  Journal  of  Anat  and  Phys.,  Vol.  XI.,  p.  2. 


THE    LIVER    AND    BILIARY   APPARATUS.  189 

The  liver-cells. — The  liver-cells  are  found  lying  within  the 
meshes  of  the  capillary  network  of  the  lobules.  If  we  bear  in 
mind  the  shape  of  the  intralobular  capillary  reticulum,  the 
arrangement  of  the  hepatic  cells  will  be  readily  understood. 
The  meshes  of  the  capillary  network  have  about  the  same 
diameter  as  the  capillaries  themselves.  Hence  it  follows  that 
the  cells  which  occupy  these  meshes  must  also  have  the  appear- 
ance of  a  reticulum.  But  inasmuch  as  the  vascular  meshes 
contain  two  or  three  liver-cells,  it  is  evident  that  two  neighbor- 
ing capillaries  must  be  separated  from  each  other  by  at  least 
one  liver-cell.  Hence,  in  sections  where  the  capillaries  are  cut 
transversely,  their  circular  openings  will  be  surrounded  by  a 
ring  of  liver-cells,  or  a  circle  of  capillaries  will  enclose  a  mass 
of  glandular  substance.  In  sections  which  cut  the  central 
vein  transversely  the  radiating  capillaries  will  enclose  radiat- 
ing rows  of  liver-cells.  (See  Fig.  81.)  These  are  either  joined 
to  one  another  by  the  intervention  of  other  liver-cells,  or 
they  are  separated  from  one  another  by  transverse  capillary 
branches. 

On  the  other  hand,  in  sections  where  the  central  vein  is  cut 
lengthwise,  the  (nearly)  parallel  intralobular  capillaries  will  ap- 
pear separated  from  one  another  by  correspond- 
ing rows  of  liver-cells.  The  glandular  substance 
of  the  liver  would  then  be  composed  of  small, 
solid  columns  or  rows  of  cells  united  to  each 
other  by  other  cells,  thus  forming  one  connected 
mass,  and  containing  within  its  meshes  the  cap- 
illary network.  In  the  fresh  state  the  liver-cells 
appear  as  spherical  or  egg-shaped  bodies,  usu- 
ally presenting  facets.  They  are  somewhat  flat- 
tened by  being  pressed  against  one  another  (Fig. 
83).  Corpuscles  possessing  processes  are  some- 

times  found.  &*  nucleus;'   ft,   with 

double  nucleus.    Prey. 

Hie  hepatic  cells  are  about  0.013—0.02  mm. 
in  diameter,  and  possess  one  or  two  nuclei,1  which  are  gener- 
ally spherical,  although  they  occasionally  appear  to  be  flat- 
tened ;  the  diameter  is  0.006—0.007  mm.  The  liver-cells  do 
not  possess  any  membrana  propria,  but  a  hardened  boundary 
layer  seems  to  exist  in  its  place.  It  is  probable  also  that  the 

1  Occasionally  three  or  five  nuclei,  especially  in  young  subjects  (Beale). 


190  MANUAL    OF   HISTOLOGY. 

cells  are  bound  together  by  a  colloid  substance,  although  this 
is  a  point  which  has  not  yet  been  definitely  settled. 

Sections  of  a  dog's  liver,  immersed  for  a  short  time  in  dilute  osmic  acid,  will 
occasionally  exhibit  a  brown  or  black  tracing  between  adjoining  cells.  Pres- 
sure on  the  cover  glass  will  part  them  and  leave  the  darkened  material  free  in 
the  field  of  vision.  I  have  satisfied  myself  that  this  tracing  is  not  of  a  nerve, 
biliary  duct,  or  connective-tissue  fibril ;  it  is  either  a  portion  of  the  boundary 
layer  of  a  liver-cell,  or,  as  I  suppose,  a  colloid  substance  between  two  cells. 
This  appearance,  however,  is  not  constant. 

The  protoplasm  is  of  a  dark  brownish  or  greenish  color.  It 
is  viscid,  and  contains  numerous  granules  of  small  size,  in  ad- 
dition to  smaller  or  larger  fat-droplets.1  In  livers  hardened  by 
chromic  acid  or  alcohol,  the  shrinkage  of  the  cells  causes  them 
to  appear  polyhedral,  and  they  also  seem  much  darker  than  in 
the  fresh  state.  If  the  portal  or  hepatic  vein  has  been  injected, 
the  cells  will  show  distinct  indentations  produced  by  the  dis- 
tended capillaries. 

When  liver-cells  are  treated  with  diluted  acetic  acid,  their 
protoplasm  becomes  pale,  while  their  nuclei  are  rendered  more 
conspicuous.  In  a  dilute  solution  of  caustic  potassa  the  cells 
swell  up,  become  rounded,  and  are  finally  dissolved.  With 
water  they  also  swell  up,  become  paler  and  more  rounded,  and 
at  length  disintegrate.  In  the  fresh  state,  by  the  addition  of 
an  indifferent  fluid  (£  per  cent,  solution  of  chloride  of  sodium, 
or  iodized  serum),  the  liver-cells  are  said  to  show  protoplasmic 
movements.  The  granular  substance  of  the  liver-cells  has 
been  shown  (by  Schiff,  in  frogs,  and  by  Nasse,  in  certain  mam- 
malia) to  consist  of  an  animal  amylum,  which  is  converted  into 
sugar  through  the  agency  of  a  peculiar  ferment. 

The  fat-droplets  may  be  either  small  in  number  and  size  or 
quite  numerous  and  large.  Not  infrequently  they  coalesce  to 
form  larger  fat-globules.  In  the  so-called  fatty  infiltration  they 
are  very  large,  and  compose  the  greater  part  of  the  cells.  The 
nuclei  are  granular,  and  where  two  or  more  of  them  occupy 
the  same  cell,  they  may  apparently  be  united  to  each  other. 

1  According  to  Kupffer  and  Klein  the  substance  of  the  cells  is  composed  of  a 
honeycombed  network,  i.e.,  an  intracellular  reticulum.  Klein  says  the  nucleus  is  lim- 
ited by  a  thin  membrane,  and  includes  an  intranuclear  network,  containing  occa- 
sionally one  or  two  nucleoli.  The  intranuclear  network  is  in  continuity  with  the 
intracellular  one,  and  the  network  of  contiguous  cells  are  in  connection  with  one 
another  (Klein  and  Smith  :  Atlas  of  Histology). 


THE    LIVER    AND    BILIARY    APPARATUS.  191 

Division  of  a  nucleus,  as  described  by  Kolliker,  I  have  never  been  able  to 
confirm.  When  two  nuclei  are  placed  in  contact,  there  may  be  an  appear- 
ance of  division,  but  the  actual  process  is  not  easy  to  see. 

Thin  liver  sections  may  be  stained  either  in  carmine  fluid  or 
luematoxylon,  and  preserved  in  glycerine  or  balsam. 

The  larger  bile-ducts. — If,  for  the  sake  of  convenience,  we 
imagine  that  the  hepatic  duct  enters  the  liver  to  be  distributed 
to  its  substance,  we  may  describe  it  as  giving  off  two  primary 
branches  at  the  transverse  fissure,  one  passing  to  the  right 
lobe,  the  other  to  the  left.  As  these  branches  continue  their 
course,  following  the  subdivisions  of  the  hepatic  artery  and 
portal  vein,  they  also  undergo  successive  divisions,  and  at 
length  enter  the  interlobular  canals.  In  this  position  their 
diameter  varies  between  0.02  and  0.03  mm. 

The  primary  branches  do  not,  however,  pass  unchanged 
into  the  liver  tissue.  They  ramify  even  before  entering-  the 
gland,  but  such  vessels  are  distributed  only  to  the  under 
surface  (Henle).  Other  biliary  ducts,  given  off  in  the  trans- 
verse fissure,  form  a  network  on  the  upper  surface,  as  may  be 
demonstrated  by  injecting  the  hepatic  duct  with  carmine-gly- 
cerine. The  branches  of  these  networks  then  enter  the  liver- 
tissue  and  ramify  throughout  it,  following  the  subdivisions  of 
the  hepatic  artery  and  portal  vein. 

As  the  divisions  of  the  hepatic  duct  diminish  in  size,  the 
thickness  of  their  walls  undergoes  proportionate  diminution. 
The  trunk  of  the  hepatic  duct  comprises  an  internal  layer 
measuring  0.15  mm.  in  thickness,  and  an  external  layer  of  0.2 
—0.3  mm.  Both  of  these  coats  are  composed,  according  to 
Henle,  of  interlacing  connective-tissue  bundles,  in  which  elas- 
tic fibres  are  freely  intermixed.  These  ducts  have  an  internal 
lining  of  cylindrical  epithelium,  which  is  0.05mm.  in  height. 
Even  where  the  branches  measure  only  0.2  mm.  in  diameter 
they  have  cylindrical  epithelium  surrounded  by  a  single  layer 
of  connective  tissue  longitudinally  disposed,  in  which  there 
are  also  muscle-corpuscles,  distinguished  by  their  long,  rod- 
shaped  nuclei  (Heidenhain).  The  most  minute  biliary  pas- 
sages consist  of  a  structureless  membrana  propria,  which  is 
lined  with  flattened  cylindrical  epithelia. 

Glands  of  the  ducts. — In  the  trunk  of  the  hepatic  duct  and 
its  subdivisions,  down  to  those  branches  of  which  the  diameter 
is  not  less  than  0.5  mm.,  the  mucous  membrane  is  provided 


192  MANUAL    OF    HISTOLOGY. 

with  numerous  irregular  excavations,  measuring  0.15 — 0.3  mm. 
in  their  long  diameter.  In  this  trunk  there  occur  also  a  great 
number  of  pores  or  orifices,  which,  on  examination,  prove  to 
be  the  mouths  of  the  passages  leading  from  simple  and  com- 
pound gland -like  bodies,  the  so-called  glands  of  the  bile-ducts. 
The  simple  glands  consist  merely  of  single  vesicles,  or  alveoli, 
with  afferent  passages,  all  of  which  are  imbedded  in  the  mu- 
cous membrane  ;  or  of  two  or  more  vesicles  with  a  single  pas- 
sage. The  compound  glands  are  formed  by  the  union  of  two 
or  more  simple  ones,  which  have  a  common  passage.  The}7"  are 
quite  large,  and  their  expanded  portions  lie  on  the  outer  sur- 
face of  the  hepatic  duct.  When  filled  by  injection  with  gela- 
tine they  are  visible  to  the  naked  eye.  The  passages  pierce 
the  walls  of  the  duct  at  an  acute  angle,  pursuing  a  course 
within  its  walls,  nearly  parallel  to  the  duct  itself  ;  the  opening 
into  the  mucous  membrane  is  therefore  quite  a  distance  from 
the  gland-vesicles.  According  to  Henle,  these  compound  glands 
are  not  found  in  the  larger  branches  of  the  hepatic  duct,  but 
they  occur  frequently  in  the  network  of  bile-ducts  situated 
in  the  transverse  fissure.  Allusion  has  already  been  made  to 
them.  The  vesicles  measure  0.04  mm.  in  diameter,  and,  like  the 
excavations  in  the  larger  branches  of  the  duct,  are  lined  with  a 
cylindrical  epithelium,  in  no  way  differing  from  that  of  the 
duct  itself ;  the  afferent  passages  also  possess  the  same  kind 
of  epithelium. 

Structures  allied  to  these  excavations  and  glands  occur  in 
small  number  in  the  bile-ducts '  which  are  found  in  the  liga- 
mentum  triangulare  and  on  the  diaphragm,  where  they  appear 
as  villous  prominences  on  the  duct- walls. 

According  to  Theile,  Weber,  and  others,  these  bile-ducts  represent  the  last 
vestiges  of  an  atrophied  liver  substance,  the  existence  of  which  dates  back  to 
infancy,  or  perhaps  to  fetal  life. 

The  excavations  in  the  larger  branches  are  either  simple 
diverticula  of  the  internal  walls,  or  the  openings  of  lateral  bile- 
ducts  ;  the  punctate  pores  are  the  orifices  of  the  outlet  pas- 
sages of  duct-glands. 

Capillary  bile-ducts  .—When  the  larger  bile-ducts,  by  con- 


1  Vasa  aberrantia  of  E.  H.  Weber. 


THE    LIVER   AND   BILIARY   APPARATUS'.  193 

tinuous  subdivision,  have  at  length  reached  the  interlobular 
canals,  in  conjunction  with  the  branches  of  the  portal  vein  and 
hepatic  artery,  they  send  capillary  branches  within  the  sub- 
stance of  the  lobule,  and  thus  form  an  intralobular  network. 
These  capillary  ducts  are  of  extreme  delicacy,  measuring  only 
from  0.001  to  0.0012  mm. 

In  order  to  demonstrate  them  fully  they  should  be  filled  by 
natural  injection.  The  substance  to  be  employed  for  this  pur- 
pose is  a  solution  of  pure  indigo-carmine.  The  animal  serving 
for  injection  (rabbit  or  dog)  should  be  secured  in  the  manner 
described  in  the  chapter  on  the  Kidney,  where  all  the  neces- 
sary manipulations  are  fully  detailed.  The  best  results  are 
obtained  by  injecting  a  cold,  saturated  solution  of  indigo- 
carmine  into  the  external  jugular  vein,  directing  the  stream 
toward  the  periphery  (brain)  ;  5  or  10  ctgms.  are  to  be  injected 
at  intervals  of  thirty  to  forty  minutes,  and  the  injection  con- 
tinued until  from  25  to  50  ctgms.  have  been  used,  the  amount 
varying  according  to  the  size  of  the  animal.  It  takes  a  longer 
time  for  the  elimination  of  indigo-carmine  through  the  capillary 
bile-ducts  than  for  the  same  process  by  way  of  the  renal  tubules, 
and  a  larger  amount  of  solution  will  therefore  have  to  be  em- 
ployed. As  soon  as  large  quantities  of  the  indigo  solution  have 
been  injected  into  the  jugular  vein,  the  animal  becomes  uncon- 
scious and  there  is  a  decrease  of  temperature ;  hence,  it  should 
be  covered  over  with  layers  of  cotton-batting.  After  a  variable 
time  (three  to  twelve  hours)  the  animal  is  killed  in  the  follow- 
ing manner  :  The  abdomen  is  opened  and  the  canula  of  a  large 
syringe  filled  with  absolute  alcohol  secured  in  the  lumen  of  the 
portal  vein ;  the  inferior  vena  cava  is  then  cut  across  above  the 
entrance  of  the  hepatic  vein,  and  the  piston  of  the  syringe 
pushed  home.  The  liver,  which  before  was  of  a  uniform  blue 
color,  -now  presents  a  marbled  appearance,  not  unlike  that  of 
malachite. 

Or,  the  portal  vein  may  be  injected  with  the  writer's  carmine- 
glycerine,  the  vena  cava  having  been  divided  as  above.  In 
either  case  the  liver  is  to  be  removed  at  once  and  placed  in  a 
vessel  containing  absolute  alcohol,  and  while  immersed  in  that 
fluid  cut  into  small  fragments.  Sections  may  then  be  made  in 
a  few  hours. 

The  arrangement  of  the  bile-capillaries  differs  in  different 
animals.  In  the  rabbit,  for  instance,  they  lie  between  the  ad- 


194 


MANUAL    OF   HISTOLOGY. 


joining  surfaces  of  two  contiguous  cells,  and  rarely  in  the 
canals  formed  by  the  edges  of  three  or  more  cells  (Hering ').  So 
that  while  the  blood-capillaries  occupy  the  canals  previously 
described,  the  bile-capillaries  form  an  independent  network  be- 
tween the  boundary  surfaces  of  the  liver-cells  (Figs.  84  and  85). 
In  cross  sections  they  may  be  seen,  appearing  as  small,  circular 


FIG.  84.  FIG.  85. 

FIGS.  84  and  85. — Injected  liver  of  rabbit.  The  narrow,  reticulated  bile-capillaries  are  shaded  with 
[longitudinal,  the  broader  blood-capillaries  with  transverse  lines.  Within  the  boundary  line  or  septum  of 
two  contiguous  cells  the  cross-section  of  a  bile-capillary  is  seen  as  a  dark  spot  or  point.  The  liver  cells 
•contain  one  or  two  nuclei.  In  Fig.  84,  the  bile-capillaries  are  slightly  distended  by  the  artificial  injec- 
tion ;  in  Fig.  85,  markedly  so.  Hering. 

openings  between  the  cells,  while  in  longitudinal  sections  they 
present  a  linear  arrangement  (Figs.  85  and  86).  In  the  dog 
this  arrangement  is  the  same,  only  here  the  bile-capillaries 
occur  more  frequently  in  the  canals  formed  by  the  edges  of  the 
lower  cells. 

According  to  Hering,  both  in  rabbits'  and  dogs'  livers  the  blood-capillaries 
are  separated  from  the  bile-capillaries  by  the  intervention  of  at  least  one  liver- 
.cell.  Livers  in  which  the  bile-capillaries  have  been  injected  by  the  natural 
method  with  indigo -carmine  do  not  always  demonstrate  this.  And  here  it  may 
be  remarked,  that  in  artificial  or  forced  injections  of  the  bile-capillaries  they 
are  always  distended  beyond  their  natural  diameters.3 

1  Hering  :  Ueber  den  Bau  der  Wirbelthierleber,  and  article  on  Liver  in  Strieker's 
Manual. 

2  Compare  Figs.  84  and  85,  after  Hering.    Even  in  Fig.  84  the  bile-capillaries  are 
larger  than  they  ought  to  be.     In  an  article  on  the  liver  by  Dr.  W.  G  Davis,  in  the 
Amer.  Jour.  Med.  Sci.,  Vol.  LXXVIII.,  the  distention  of  the  capillaries  is  excessive. 


THE   LIVER   AND   BILIAEY   APPARATUS. 


195 


By  conjoined  natural  injection  of  the  bile-capillaries  and 
artificial  injection  of  the  portal  system  with  carmine-glycerine 
by  the  methods  above  detailed,  very  gratifying  results  are  ob- 
tained.    Care  must  be  taken, 
however,  not  to  use  too  much 
force  during  the  process  of  in- 
jection, and   only    such  por- 
tions of  the  liver  should  be 
chosen  for  sections  as  show, 
by  their  red  color,   a  perfect 
filling  of  the  portal  branches. 

While  the  elimination  of 
the  indigo-carmine  is  taking 
place  within  the  liver  of  the 
living  animal,  the  bile-capilla- 
ries probably  contain  the  salt 
in  a  soluble  form.  The  addi- 
tion of  absolute  alcohol  at 
once  precipitates  this  color- 
ing reagent  in  the  form  of 
exceedingly  fine  stellate  crys- 
tals, or  as  finely  granular  mat- 
ter, which  may  in  some  meas- 
ure account  for  the  angular 
character  of  the  biliary  capil- 
laries, as  seen  in  such  specimens.  Gentle  curves,  such  as  are 
represented  in  Fig.  85,  never  appear.  The  constringing  action 
of  the  alcohol  on  the  liver-cells  has  unquestionably  some  effect, 
and  therefore  modifies  the  normal  appearance. 

Natural  injections  further  show  the  great  preponderance  of 
the  biliary-  over  the  blood-capillaries.  In  the  liver  of  a  dog, 
for  instance,  each  liver-cell  seems  suspended  within  two  or 
three  (rarely  four)  bile-capillaries,  and  where  the  latter  are 


PIG.  86. — Liver  of  a  three-months'  child,  hard- 
ened in  chromic  acid.  The  capillaries  are  filled  with 
red  blood-corpuscles  (indicated  by  colorless  rings)  and 
a  few  leucocytes.  The  cross  section  of  a  bile-capillary 
is  shown  within  the  boundary  line  of  any  two  con- 
tiguous cells.  A  similar  cross  section  is  shown  in 
the  canal  formed  by  three  adjoining  liver-cells. 


One  need  only  compare  Fig.  3  in  Davis's  article  with  Fig.  84  of  Hering's,  which,  by 
the  way,  is  a  good  illustration. 

The  first  to  describe  the  intralobular  network  of  bile-capillaries  were  Andrejevic 
(Ueber  der  feineren  Bau  der  Leber.  Wiener  Sitzungsbericht,  1861)  and  MacGillavry 
(Zur  Anat.  d.  Leber.  Wiener  Sitzungsbericht,  1864).  Chronszewski  was  the  first  to 
inject  the  bile-capillaries  by  natural  injection  (Virchow's  Archiv,  Bd.  35).  MacGillavry 
Chronszewski,  Budge,  and  others,  described  the  bile-capillaries  as  possessing  true 
walls. 


196 


MANUAL    OF   HISTOLOGY. 


FIG.  87.—  Capillary  bile-ducts  of  a  rabbit, 
distended  by  artificial  injection  :  1,  a  portion 
of  a  lobule  ;  or,  central  vein  ;  6,  6,  interlobular 
veins  ;  c,  c,  bile-ducts  ;  d,  d,  blood-capillaries  ; 
e,  e,  bile-capillaries. 


joined  together  the  calibre  of  the  capillary  is  markedly  in- 
creased. Sections  made  parallel  to  the  external  surface  of  the 
liver,  immediately  under  the  capsule,  generally  cut  the  central 

vein  transversely,  and  such  sec- 
tions show  that  the  bile-capillaries 
possess  a  somewhat  radial  course 
(Pig.  87).  Human  livers  can  rarely 
be  obtained  in  a  fresh  state,  and 
examinations  of  their  bile-capil- 
laries are  therefore  attended  with 
difficulty. 

Do  the  bile-capillaries  possess 
walls  of  their  own  f — This  ques- 
tion must  be  answered  in  the 
affirmative.  In  specimens  where 
the  bile- capillaries  have  been  in- 
jected by  the  natural  method, 
cross  sections  of  such  capillaries 
will  demonstrate,  with  high  pow- 
ers, that  there  is  a  dot  of  blue  indigo-carmine  surrounded  by 
a  distinct  circle  which  is  perfectly  transparent  and  in  marked 
contrast  to  the  somewhat  yellowish  color  of  the  adjoining 
liver-cells.  (See  Fig.  88.)  It  is  more  difficult  to  see  this  in 
sections  which  cut  the  capillaries  in  their  longitudinal  diam- 
eters, but  where  two  or  more  capil- 
laries unite  this  halo  is  again  seen. 
That  this  appearance  is  due  to  the  pres- 
ence of  a  true  wall  seems  clear,  but  all 
doubts  will  be  dispelled  by  watching 
the  diffusion  which  takes  place  in  such 
a  section  on  the  addition  of  a  few  drops 
of  water  under  the  cover  glass.  The 
indigo-carmine  becomes  dissolved  in 
the  water,  forming  a  deep  blue  liquid 
which  stains  the  surrounding  cells  and 
vessels  of  a  uniform  color.  While 
watching  a  bile-capillary  during  the 
progress  of  this  action  it  appears  to 

stand  out  more  prominently  than  before,  and  its  walls  become 
more  distinct.  In  a  few  moments  the  cells  will  have  become 
swollen  by  the  imbibition  of  water,  and  the  picture  gradually 


FIG.  88.— Liver  of  the  dog.  Nat- 
ural injection  of  bile  -  capillaries, 
showing  double  contour  of  the  capil- 
laries, which  are  only  partly  filled 
with  injection.  Cross  sections  of 
the  capillaries  show  a  dot  of  indigo- 
carmine  surrounded  by  a  distinct 
halo.  The  woodcut  does  not  show 
this  satisfactorily.  In  the  specimen 
the  lines  corresponding  to  the  walls 
of  the  capillaries  are  of  the  utmost 
delicacy.  Magnified  450  diam. 


THE    LIVER    AND    BILIARY    APPARATUS.  197 

fades,  until  at  length  it  would  be  difficult  to  even  locate  the 
original  seat  of  the  capillary.  I  have  verified  this  over  and 
over  again.  The  capillary  walls  seem  to  be  structureless ;  at 
least  with  a  power  of  1,400  diameters  I  have  been  unable  to 
detect  any  structure.  The  membrana  propria  of  the  inter- 
lobular  bile-ducts  is  continued  on  to  the  capillaries  within  the 
lobule. 

Hering,  Henle,  and  others  do  not  believe  that  the  bile-capillaries  possess 
walls  of  their  own,  but  suppose  them  to  be  contained  within  the  boundary- 
surface  of  the  liver-cells,  the  latter  taking  the  place  of  the  epithelium  of  the 
interlobular  bile-ducts.  Henle  further  quotes  Schweigger-Seidel  (in  the  Archiv 
far  path.  AnaL  und  Phys.,  XXVII.,  505,  1863),  who  injected  the  bile-capillaries 
with  faintly  colored  gelatine,  and  showed  that  by  warming  the  slide  the  gela- 
tine dissolved  without  leaving  any  residue  whatever.  From  what  has  been 
said  of  artificial  injections,  and  recognizing  the  extreme  delicacy  of  the  bile-cap- 
illaries, it  is  not  surprising  that  this  result  was  obtained  after  injecting  a  warm 
solution  of  gelatine  into  the  capillaries.  The  walls  of  these  capillaries  are 
homogeneous  and  exceedingly  delicate,  so  that  they  are  destroyed  by  a  mod- 
erate degree  of  heat.  Very  soon  after  death  they  undergo  a  sort  of  liquefac- 
tion, and  what  was  before  a  vessel  with  true  walls  is  now  an  open  channel, 
through  which  an  artificial  fluid  can  be  made  to  force  its  way. 

At  first  the  elimination  of  the  indigo-carmine  takes  place 
in  the  bile- capillaries  on  the  external  border  of  the  lobule, 
and  somewhat  later  the  capillaries  about  the  central  vein  be- 
come filled.  Neither  the  protoplasm  of  the  liver-cells  nor  their 
nuclei  ever  become  stained  with  the  blue  solution  during  the 
process  of  elimination  ;  such  coloring  would  be  the  result  of 
post-mortem  diffusion.  But  the  cylindrical  epithelium  of  the 
glands  is  colored  blue,  and  indubitably  these  glands  excrete 
the  indigo-carmine,  as  do  the  cells  of  the  convoluted  tubules  of 
the  kidney.  Whether  they  secrete  any  substance  during  life, 
or  what  that  substance  may  be,  has  not  yet  been  determined. 

Theile,  Kolliker,  and  Kiernan  suppose  that  these  glands  secrete  a  mucous 
substance  which  becomes  mixed  with  the  bile.  Henle  regards  these  glands 
and  excavations  as  reservoirs  which  are  occasionally  filled  with  bile.  From 
what  has  been  said  above  it  would  appear  that  the  cylindrical  epithelium  of 
the  glands  eliminates  the  indigo-carmine,  and  hence  we  may  suppose  that 
they  secrete  some  fluid  or  substance  during  life. 

The  gall-bladder. — The  walls  of  the  gall-bladder  are  about 


198  MANUAL    OF   HISTOLOGY. 

2  mm.  thick,  and  are  composed  of  three  coats : '  an  internal, 
mucous  and  muscular ;  a  middle,  of  connective  tissue ;  and 
an  external,  the  serous.  The  internal  coat,  0.4  to  0.5  mm. 
thick,  is  composed  of  alternating  layers  of  connective  tissue 
and  smooth  muscle  fibres,  the  most  internal  being  a  layer  of 
connective  tissue  which  contains  a  fine  meshed  capillary  net- 
work. The  connective  tissue  is  dense  and  the  muscle  fibres  are 
arranged  in  the  form  of  interlacing  bands.  The  internal  sur- 
face is  lined  by  a  layer  of  cylindrical  cells  bearing  a  thickened, 
striated  edge,  and  the  surface  is  traversed  by  a  network  of 
small  intersecting  ridges,  forming,  as  it  were,  a  sort  of  lattice- 
work. The  middle  coat,  0.5  to  1  mm.  thick,  is  formed  of  con- 
nective tissue,  the  meshes  of  which  are  wider  on  the  internal 
than  at  the  external  surface.  This  coat  contains  the  larger 
vessels  and  nerves.  The  external,  or  serous  coat  is  thin,  and 
consists  of  a  layer  of  dense  connective  tissue  and  peritoneum. 
A  few  mucous  glands 2  are  found  scattered  here  and  there  in 
the  walls  of  the  gall-bladder.  Sections  from  this  organ,  hard- 
ened in  alcohol,  may  be  stained  with  the  carmine  or  picro-car- 
mine  solution  and  mounted  in  glycerine  or  balsam. 

The  cystic  and  common  ducts  resemble  in  structure  the 
hepatic  duct.  The  inner  surface  of  the  former  is  thrown  into 
crescentic  ridges,  and  in  the  region  of  the  neck  of  the  gall- 
bladder the  connective  tissue  of  the  internal  coat  shows  a 
circular  arrangement.  The  ducts  contain  no  muscle  fibres. 

The  lymph-vessels. — These  may  be  divided  into  a  series 
of  superficial  and  deep  channels.  The  former  are  situated  in 
the  capsule  of  the  .liver  and  form  a  capillary  reticulum  with 
small  meshes,  the  larger  branches  of  which  accompany  the 
arteries  in  pairs  and  communicate  with  each  other  by  trans- 
verse anastomoses.  They  are  found  in  Glisson's  capsule,  and 
they  also  form  a  network  somewhat  larger  meshed  than  the 
preceding.  They  accompany  the  hepatic  artery  and  portal 
vein  and  their  branches  into  the  interior  of  the  liver,  and  form 
anastomoses  with  the  superficial  lymph- vessels.  The  lymph- 
canals  may  easily  be  injected  with  colored  material  (carmine- 
glycerine)  by  filling  a  large  hypodermic  syringe  with  the  liquid 
and  injecting  one  of  the  larger  lymph-vessels  in  the  hilus  of 


1  Henle  :  Eingeweidelehre. 

2Luschka:  Virchow's  Archiv,  1857,  and  Zeitschr.  f.  rat.  Med.,  1858. 


BIBLIOGRAPHY.  199 

the  liver.  The  syringe  may  be  refilled  three  or  four  times 
without  removing  the  canula,  and  the  injection  must  be  made 
in  the  direction  of  the  normal  lymph-current.  In  this  way 
the  colored  liquid  will  flow  backward  into  the  smaller  vessels. 
During  the  injection  of  the  larger  branches  their  proximal  ends 
should  be  secured  by  clamps  or  ligatures. 

The  nerves  of  the  liver  enter  the  organ  at  the  hilus  and  fol- 
low the  course  of  the  vessels.  They  are  composed  mostly  of 
non-medullated  elements,  a  few  medullated  fibres  being  found 
in  the  larger  branches.  They  cannot  be  traced  into  the  lobules. 


BIBLIOGRAPHY. 

KIERNAN.     Anat.  and  Phys.  of  the  Liver.     Philos.  Trans.     1833. 

LAMBRON.     Archiv.  gen.     1841. 

KRUKENBERG.     Mailer's  Archiv.     1843. 

WEBER,  E.  H.     Muller's  Archiv.     1843.     Program,  col.  fasc.,  II.     Lips.,  1851. 

THEILE.     Wagner's  Handworterb.    Bd.  II.     1844. 

RETZIUS.     Miiller's  Archiv.     1849. 

WEDL.     Sitzungsber.  d.  Wiener  Akad.     1850. 

RAINEY.     Quart.  Jour.  Microsc.  So.     Vol.  1.     1853. 

GERLACH.     Gewebelehre.     1854. 

BEALE.     Philos.  Trans.     1855.    Anat.  of  the  Liver.   1856.   Archives  of  Med.    Vols. 

I.  and  II. 

VIRCHOW.    Virchow's  Archiv.     Bd.  XI.    1857. 
LUSCHKA.     Henle  u.  Pfeuffer's  Zeitsch.     Bd.  IV.    1858. 
BUDGE.     Reichert  u.  Du  Bois-Reymond's  Archiv.    1859. 
His.     Zeitschft.  f.  wiss.  Zoologie.     Bd.  X.     1860. 
WAGNER,  E.     Archiv  d.  Heilkunde.    1860.    Oester.  Zeitschrft  f.  prak.    Heilkunde, 

1861. 
EBERTH.     Zeitschrft.  f.  wiss.  Zoologie.     1860.     Med.  Centralbl.     1866.     Virchow's 

Archiv.     1867.     Schultze's  Archiv  f.  mik.  Anat.     Bd.  III. 
ANDREJEVIC.     Sitzungsber.  d.  Wiener  Akad.     1861. 
RIESS.     Reichert  u.  Du  Bois-Reymond's  Archiv.     1863. 
SCHWEIGGER-SEIDEL.     Reichert  u.  Du  Bois-Reymond's  Archiv.    1863. 
MACGILLAVRY.     Sitzungsber.  der  Wiener  Akad.     1864. 
IRMINGER.     Zeitschft.  f.  wiss.  Zoologie.     Bd.  XVI.     1866. 
CIIRONSZEWSKI.     Virchow's  Archiv.     Bd.  XXXV.     1866. 
HERING.      Sitzungsber.  d.  Wiener  Akad.     1866.    Strieker's    Handbuch.      Bd.  I. 

1871. 

KOLLIKER.     Handbuch  d.  Gewebelehre.     1867. 
VON  BIESIADECKI.     Sitzungsber.  d.  Wiener  Akad.     1867. 
HETDENHAIN.     Studien  aus  d.  phys.  Instituts  z.  Breslau.     Heft  IV.    1868. 
KISSELEW.     Med.  Centralbl.     1869. 


200  MANUAL    OF   HISTOLOGY. 

PFLUGER.     Pfliiger's  Archiv.    Bd.  II.     1869.     u.  IV.     1871. 

HENLE.     Eingeweidelehre.     1873. 

LEGROS.     Jour,  de  1'anat.  et  de  la  phys.    1874. 

COHNHEIM  u.  LITTEN.     Virchow's  Archiv.    Bd.  LXVI.    1876. 

EWALD  u.  KUEHNE.     Verhand.  Naturhist.  med.  Vereins  zu  Heidelberg.     1  Bd.   5 

Hft.     1876. 

KOLATSCHEWSKY.     Schultze's  Archiv.    Bd.  XIII.    1876. 
TURNER.     Journ.  of  Anat.  and  Phys.     Vol.  XI.    1877. 
WENDT.     Med.  Centralblatt     No.  15.     1878. 
DAVIS.     Amer.  Jour.  Med.  So.    Vol.  LXXVIII.    1879. 
FRITSCH.     Archiv.  fur  Anat.  und  Phys.     Phys.  Abtheil.    1879. 
KLEIN  and  SMITH.    Atlas  of  Histology.    Part  X.    1879—1881. 


CHAPTER  XIV. 

THE  KIDNEY. 

Br  ABRAHAM  MAYER,  M.D., 

Curator  of  the  Manhattan  Eye  and  Ear  Hospital,  New  York  City. 

General  plan  of  structure. — The  glandular  substance  of  the 
kidney  is  divided  into  two  parts,  an  external  or  convex  por- 
tion, called  the  cortical  substance,  or  cortex,  and  an  internal 
or  concave  portion,  the  'medullary  substance,  or  medulla. 
This  division  can  be  readily  seen  by  cutting  a  kidney  into  two 
equal  parts  in  the  line  of  its  long  diameter.  An  intermediate 
zone,  which  separates  the  cortical  from  the  medullary  sub- 
stance, is  called  the  boundary  layer  of  the  kidney.  The  whole 
organ  is  enveloped  in  a  fibrous  membrane,  the  capsule. 

The  medullary  substance  contains  the  pyramids  of  the  kid- 
ney, and  is  therefore  also  called  the  pyramidal  portion.  The 
apex  of  each  pyramid,  the  papilla,  projects  into  a  special  arm 
of  the  renal  pelvis,  viz.,  a  calyx;  the  base  or  expanded  por- 
tion is  directed  toward  the  cortical  substance,  and  sends  pro- 
longations into  the  latter. 

An  examination  of  the  cortical  substance  shows  it  to  be 
composed  of  two  distinct  varieties  of  tissue,  running  parallel 
to  one  another  toward  tlie  free  surface.  One  has  a  fibrous  ap- 
pearance, and  is  composed  of  cylindrical  cords.  It  is  a  con- 
tinuation of  the  pyramids.  These  pyramidal  prolongations  * 
(Henle)  are  also  called  medullary  rays  (Fig.  89).  The  other 
portion,  situated  between  the  prolongations,  is  a  granular-look- 
ing material,  called  the  cortical  substance  proper,  or  labyrinth 
of  Ludwig*  The  latter  contains  numerous  small  bodies, 
which  are  of  a  distinctly  red  color  when  there  is  a  large 

1  Ludwig  und  Zawarykin  :  Zeitschrft.  f  iir  rat.  Med.,  1863.     They  are  also  called 
the  prolongations  of  Ferrein. 

2  Ludwig :  Strieker's  Manual,  p.  461. 


202 


MANUAL    OF   HISTOLOGY. 


amount  of  blood  in  the  kidney  ;  they  are  the  MalpigJiian 
bodies,  or  glomeruli  (Fig.  89,  E). 

The  boundary  layer '  is  characterized  by  numerous  blood- 
vessels, some  of  which,  unite  to  form  an  arcade  (Fig.  89,  C), 
which  is  parallel  to  the  convex  surface  of  the  kidney,  and  from 
which  branches  are  given  off  to  the  cortical  substance  proper. 

The  renal  artery,  before  it  enters  the 
hilum  of  the  kidney,  divides  into 
branches,  which  pierce  the  medulla 
between  the  pyramids  and  ascend 
toward  the  cortical  substance  until 
they  reach  the  boundary  layer.  Here 
they  divide  obliquely  or  at  right 
angles  to  give  off  smaller  branches, 
which  have  the  direction  and  arched 
ppearance  above  referred  to  (Fig. 
89,  C).  These  arched  vessels  then 
send  off  the  branches  already  men- 
tioned, which  traversing  the  centres 
of  the  cortical  substance  proper,  at 
right  angles  to  the  parent  stem  (Fig. 
89,  D),  extend  almost  to  the  capsule 
of  the  kidney.  On  their  way  they  in 
turn  give  off  smaller  twigs,  each  of 
which  bears  a  glomerulus  upon  its 
extremity  (Fig.  89,  E).  In  this  way 
there  is  an  alternate  arrangement  of 
pyramidal  prolongation  and  cortical 
substance  proper  (Fig.  90).  Though 
he  pyramidal  prolongations  almost 
reach  the  capsule  of  the  kidney, 
they  never  quite  touch  it,  being  sep- 
arated by  the  interposition  of  some  cortical  substance  proper 
(Fig.  89). 

Specimens  for  study  should  be  made  from  a  fresh  kidney, 
in  which  the  renal  artery  has  been  injected  with  carmine-gela- 
tine, the  whole  organ  having  been  subsequently  immersed  in 
alcohol  of  50  per  cent,  strength.  When  in  that  fluid  it  is  to  be 
divided  into  four  or  more  parts,  allowed  to  remain  therein  for 


FIG.  89. —  Human  kidney.  Vertical 
section  through  cortical  and  medullary 
substances :  A,  branch  of  renal  artery ; 
B,  vein,  immediately  beneath  former,  but 
hardly  visible  in  the  figure;  C,  arched 
arterial  branches  in  the  boundary  layer ; 

D,  artery  of  the  cortical  substance  proper ; 

E,  Malpighian    bodies  or  glomeruli :   F, 
medullary  rays  or  pyramidal  prolonga- 
tions ;  G,  vessels  of  the  medulla,  the  vasa 
recta,   x  10. 


1Henle:  Grenzschicht,  Eingeweidelehre. 


THE   KIDNEY. 


203 


twenty-four  hours,  afterward  transferred  to  stronger  alcohol, 
then  to  absolute  alcohol,  and  finally  mounted  in  dammar  or 
balsam.  Vertical  sections  show  the  arrangement  represented 
in  Figs.  89  and  90  ;  transverse  sections,  the  appearance  of 
Fig.  92. 

The  substance  of  the  kidney  is  composed  of  secreting  and 
collecting  tubules,  vessels,  and  a  stroma,  which  fills  the  inter- 


Fro.  90.— Human  kidney.  Vertical  section  through  cortical  portion :  A,  pyramidal  prolongation  ;  B, 
cortical  substance  proper ;  C,  artery ;  D,  glomerulus.     x  64. 

spaces  between  the  tubules,  and  is  more  abundant  in  the  med- 
ullary than  in  the  cortical  substance.  In  human  adults  this 
connective  material  is  found  in  small  quantity  and  is  a  sort  of 
colloid  substance.  In  the  lower  animals  it  is  more  abundant, 
and  assumes  the  character  of  real  connective  tissue.  In  young 
infants  there  is  said  to  be  a  greater  proportionate  amount  of 
this  tissue  than  in  subsequent  life. 

The  renal  tubules. — The  tubules  are  found  both  in  the  corti- 


204 


MANUAL    OF   HISTOLOGY. 


cal  and  medullary  substances  ;  they  are  of  different  diameters 
and  pursue  either  a  straight  or  tortuous  course.  Some  have  a 
basement  membrane  (membrana  or  tunica  propria),  on  which 
the  epithelium  rests ;  others  appear  to  have  none.  The  tu- 
bules are  clothed  with  epithelium  of  different  varieties.  Speci- 
mens' should  be  made  from  a  kidney  that  has  lain  for  twenty- 
four  hours  in  a  5  per  cent,  solution  of  chromic  acid.  A  small 


FIG.  91.— Schematic  representation  of  the  kidney :  A,  medulla ;  B,  boundary  layer ;  C,  cortical  por- 
tion ;  a,  renal  artery ;  b,  renal  vein ;  c,  artery  penetrating  cortex ;  D,  capsule  enclosing  glomerulus ;  E, 
capillaries ;  F,  convoluted  tubules  of  first  order ;  G,  looped  tubule,  descending  branch  ;  H,  looped  tubule, 
ascending  branch ;  I,  convoluted  tubule  of  second  order ;  J,  collecting  tubule ;  K,  vasa  recta. 

piece  of  the  gland  is  to  be  placed  on  a  slide,  and  a  drop  of  glycer- 
ine added ;  the  tubules  may  be  isolated  by  teasing  with  needles. 
In  Fig.  91  there  is  a  schematic  representation  of  the  vascular 
distribution  and  course  of  the  tubules  in  one  of  the  pyramids. 
Each  tubule  takes  its  origin  in  an  expansion  that  surrounds 
the  glomerulus,  and  is  called  Bowman ' s  or  Mullens  capsule.1 

1  Miiller,  in  1830,  described  the  capsules,  but  regarded  them  as  vesicles  which  had 
no  connection  whateyer  with  the  uriniferous  tubules.  Bowman,  in  Philosoph.  Trans; 
act.,  1843. 


THE    KIDNEY.  205 

It  is  round  or  elliptical  in  shape,  and  has  a  diameter  of  about 
0.2  mm.  Where  the  capsule  empties  its  contents  into  the 
tubule,  there  is  a  slight  constriction  known  as  the  neck ;  it  is 
very  distinct  in  some  of  the  lower  animals.  The  canal  then  en- 
larges and  begins  to  pursue  a  tortuous  course  in  the  cortical 
substance  ;  it  is  now  called  a  convoluted  tube 1  (Fig.  91,  F).  It 
next  undergoes  sudden  diminution  in  size  and  passes  straight 
through  the  medulla  until,  at  a  variable  point,  it  bends  upon 
itself,  forming  a  loop ;  then,  ascending,  it  increases  in  calibre,  and 
in  the  cortical  substance  becomes  convoluted  for  the  second  time. 
Those  canals  that  are  nearest  the  glomeruli  are  called  convo- 
luted tubules  of  the  first  order,  the  others  convoluted  tubules 
of  the  second  order.  Between  these  two  are  the  looped  tubules 
of  ffenle,  just  described,  each  being  divided  into  a  descending 
and  ascending  branch  (Fig.  91,  G  and  H).  The  convoluted 
tubules  of  the  second  order  terminate  by  emptying  into  tubules 
of  greater  diameter,  called  collecting  tubules,*  which  descend 
through  the  cortical  and  medullary  substances,  and,  receiving 
other  collecting  tubules  on  the  way,  finally  empty  into  the 
pelvis  of  the  kidney  (Fig.  91,  J).  * 

At  the  base  of  each  pyramid  there  are  a  vast  number  of  col- 
lecting tubules,  but  as  they  successively  empty  into  larger 
collecting  tubes,  the  area  they  occupy  is  thereby  diminished  ; 
at  the  apex  of  the  papillae,  where  they  ultimately  discharge 
the  urine  into  the  pelvis  of  the  kidneys,  there  are  only  about 
twenty  in  number.  This  gradual  coalescence  of  the  tubes  gives 
to  the  pyramids  a  conical  shape,  but  the  breadth  of  the  base  is 
also  partly  due  to  the  presence  of  the  looped  tubules  which 
pass  down  into  the  pyramids  for  a  varying  depth. 

The  larger  collecting  tubules  may  be  readily  injected  with 
Beale's  blue  fluid 3  or  carmine-gelatine,  either  directly  or  from 
the  ureters  ;  it  will  be  found,  however,  that  the  injection  will 
seldom  extend  beyond  the  looped  tubules,  owing  to  the  small 
diameter  of  the  descending  branches. 

1  Tubulus  contortus.  2  Straight  tubules  of  Bellini. 

3  Glycerine,  pure,  2  oz.  ;  tr.  perchloride  iron,  10  drops  ;  ferrocyan.  potassium,  3 
grains  ;  strong  hydrochl.  acid,  3  drops ;  water,  1  oz.  Mix  the  tincture  of  iron  with 
one  ounce  of  the  glycerine ;  and  the  f  errocyanide  of  potassium,  first  dissolved  in  a  little 
water,  with  the  other  ounce  ;  mix  gradually,  and  shake  during  admixture  ;  add  the 
iron  to  the  ferrocyanide ;  lastly,  add  the  water  and  hydrochloric  acid.  Beale  : 
Microscope,  p.  87. 


206  MANUAL    OF   HISTOLOGY. 

Bowman's  capsule  is  composed  of  a  structureless  basement- 
membrane  surrounding  each  glomerulus.  Upon  the  inner  sur- 
face of  these  capsules  is  a  continuous  layer  of  flat,  epithelioid 
cells,1  which  are  continued  over  the  glomerulus  itself.2  Occa- 
sionally an  epithelioid  cell  may  be  seen  between  the  vessels  of 
the  coil  composing  the  glomerulus. 

Each  capsule  is  pierced  by  two  vessels,  called,  respectively, 
afferent  and  efferent.  The  former  enters  the  capsule  and  forms 


-D 


FIG.  92.— Human  kidney.  Transverse  section  of  cortical  portion,  showing  the  alternating  arrangement 
of  pyramidal  ray  and  cortical  substance  proper :  A,  A,  pyramidal  rays :  B,  convoluted  tubule :  C,  elom- 
erulus ;  D,  D,  arterial  vessels,  x  55. 

the  glomerulus,  while  the  latter  makes  its  exit  close  to  the  en- 
•trance  of  the  former.  The  layer  of  epithelium  above  described 
passes  over  from  the  inner  surface  of  the  capsule  on  to  the 
glomerulus  about  the  points  of  entrance  and  exit  just  men- 
tioned. On  the  opposite  side,  the  capsule  becomes  continuous 
with  a  convoluted  tubule.  To  obtain  specimens,  the  renal  artery 
of  a  fresh  kidney  should  be  injected  with  blue  gelatine  and  then 
placed  in  alcohol.  Vertical  and  transverse  sections  of  the  cor- 
tical substance  may  then  be  made.  They  should  be  stained  in 
carmine  and  examined  in  glycerine,  or  the  artery  may  be  in- 
jected with  absolute  alcohol  and  the  sections  stained  as  above. 
The  epithelium  of  the  tubules. — The  basement-membranes 
of  the  convoluted  tubules  of  the  first  order  are  in  direct  con- 
tinuation with  the  basement-membranes  of  the  capsules.  Their 
diameter  averages  0.04  mm.  The  epithelium  of  these  canals  is 

1  Schweigger-Seidel :  Die  Nieren.    Halle,  1865.   Henle  :  Eingeweidelehre,  p.  329. 
Heidenhain :  Zur  anat.  d.  Nieren,  in  Schultze's  Archiv,  Bd.  X.,  Hft.  I.    Mayer :  His- 
tology of  the  Kidney,  Dis.  Inaug.,  1876.     Also  Bowman,  Johnson,  Frerichs,  etc. 

2  Gerlach,  Heidenhain. 


THE   KIDNEY. 


207 


peculiar,  and  was   first  correctly  described  by  Heidenhain. 
According  to  this  writer,  the  greater  part  of  the  cell-protoplasm 
assumes  the  form  of  small,  cylindrical  bodies,  the  so-called 
rods  of  HeidenJiaiU)  giving  the  epithelium  a  stri- 
ated appearance  (Fig.  93). 

To  exhibit  these  appearances,  the  cortical  sub- 
stance of  a  dog's  or  rabbit's  kidney  should  be 
cut  into  small  pieces  and  immersed  for  twenty- 
four  hours  or  more  in  a  5  per  cent,  solution  of 
the  neutral  chromate  of  ammonia.  After  this 
time  has  elapsed,  a  small  piece  of  the  gland  is  to 
be  placed  on  a  slide  and  a  drop  of  glycerine 
added  ;  the  specimen  may  then  be  teased  and  ex- 
amined. Portions  of  the  convoluted  tubules  will 
be  found  floating  about  in  the  glycerine,  and 
should  be  closely  scrutinized.  By  this  mode  of 
preparation,  individual  epithelioid  corpuscles  can- 
not be  recognized  ;  on  the  contrary,  they  seem 
to  merge  with  one  another.  The  tubule  may  be 
regarded  as  made  up  of  rods  transversely  dis- 
posed,  with  nuclei  embedded  in  a  pulpy  mass 
that  appears  to  fill  its  lumen,  the  whole  envel- 
oped  by  the  membrana  propria.  The  rods  sur- 
round the  nuclei,  and  are  not  all  of  the  same  length.  They 
appear  to  be  hollow,  as  shown  by  their  sometimes  containing 
fatty  granules.  Here  and  there  in  the  specimen  a  separate 
corpuscle  will  present  itself  to  the  eye;  in 
such  instances  the  rods  can  readily  be  made 
out  (Fig.  94,  A).  In  the  kidney  of  the  rat 
these  bodies  may  be  isolated  with  little  diffi- 
culty (Fig.  94,  B).  At  one  end  the  rods  rest 
against  the  membrana  propria,  to  which  they 
are  attached  by  a  colloid  material  ;  their  other 
extremity  is  lost  in  the  protoplasm  of  the  cap- 
sale,  which  latter  lies  internal  to  them  and 
appears  to  have  the  character  of  a  pulpy  mass 
containing  nuclei.  In  the  dog,  the  nucleus  of 
each  cell  is  about  midway  between  the  lumen 
and  the  membrana  propria.  It  is  surrounded  by  rods  (Fig. 
94,  A).  In  the  rat  this  is  not  the  case  (Fig.  94,  B).  Assuming 
that  the  rods  begin  at  the  membrana  propria,  they  are  directed 


%£*?&.*" 


A- 


x°lioB'  kidn'y  °f  rat* 


208  MANUAL    OF   HISTOLOGY. 

toward  the  centre  of  the  lumen  of  the  tubule,  and  the  distance 
between  any  two  adjoining  rods  at  the  periphery  is  necessarily 
greater  than  at  the  centre.  For  the  same  reason,  also,  the  rods 
are  more  distinctly  defined  in  the  former  situation  ;  the  micro- 
meter screw  will  have  to  be  used  in  tracing  them  inward. 

Transverse  sections  of  the  cortical  substance  may  be  made 
by  freezing  small  pieces  which  have  been  immersed  in  a  solu- 
tion of  the  neutral  chromate  of  ammonia.  Such  sections  should 
be  examined  in  glycerine,  or,  better,  in  a  saturated  solution  of 
the  chloride  of  potassium  in  glycerine.1  The  radial  direction 
of  the  rods  is  beautifully  seen  in  such  specimens  (Fig.  95,  C), 


FIG.  95. — Kidney  of  dog.  Transverse  section  through  the  medullary  portion,  about  midway  between 
the  apex  and  boundary  layer.  Neutral  chromate  of  ammonia  preparation  :  A,  blood-vessel ;  B,  looped 
tubule,  descending  portion ;  C,  looped  tubule,  ascending  portion ;  D,  collecting  tubule ;  E,  connective 
tissue,  x  300. 

and  the  individual  cells  are  more  clearly  defined.  Another 
method  of  exhibiting  these  rod  epithelia  is  to  inject  the  artery 
or  vein  of  a  fresh,  bloodless  kidney  with  a  cold  saturated  solu- 
tion of  the  chloride  of  potassium,  then,  after  placing  the  whole 
organ  in  alcohol,  divide  it  in  small  pieces  under  that  fluid. 
After  a  day  or  two  sections  may  be  made  ;  they  then  should  be 
immersed  for  a  short  time  in  absolute  alcohol  and  clarified  by 
oil  of  turpentine.  Such  specimens  show  the  epithelium  to 
perfection  and  may  be  preserved  for  a  considerable  time.  Per- 
manent specimens  can  be  made  by  substituting  resinous  turpen- 

1  The  glycerine  should  be  heated  in  a  porcelain  evaporating-dish,  the  chloride  of 
potassium  added,  and  the  whole  mixture  stirred  for  several  minutes  with  a  glass  rod. 
The  glycerine  is  ready  for  use  after  cooling. 


THE    KIDNEY.  209 

tine l  for  the  common  oil.  The  renal  artery  or  vein  may  also 
be  injected  with  absolute  alcohol,  and  sections  prepared  as 
above.  But  the  epithelium  suffers  in  this  way,  for  the  alcohol 
causes  the  rods  to  shrink,  and  the  colloid  substance  between 
the  rods  coagulates.  Still,  the  striated  appearance  is  seen  near 
the  membrana  propria.  Another  fact  which  seems  to  have  es- 
caped Heidenhain  is  that  alcohol  so  injected  causes  the  nuclei 
of  the  cells  to  recede  toward  the  membrana  propria  by  its 
action  on  the  rods. 

The  action  of  water  on  the  rods  is  peculiar.  A  fresh  kidney 
must  be  used  and  a  portion  of  the  cortical  substance  placed  on 
a  slide,  together  with  a  drop  of  water ;  it  is  then  to  be  teased 
with  needles  and  immediately  examined.  At- first  the  rods  are 
not  distinctly  brought  into  view,  but  they  soon  appear  with 
their  contours  sharply  delineated.  This  appearance,  however, 
does  not  last  very  long,  for  the  epithelium  soon  imbibes  water, 
swells,  and  then  forms  an  indistinct  mass. 

In  the  neck  of  the  convoluted  tubules  of  the  frog,  coluber, 
etc.,  the  epithelium  is  ciliated.  In  the  frog  the  cilia  have  great 
length,  but  the  convoluted  tubules  do  not  have  the  rod  epithe- 
lium. In  the  dog,  cat,  rabbit,  etc.,  the  rod  epithelium  begins 
at  the  neck  of  the  tubule  and  is  continued  as  far  as  the  loops. 

The  convoluted  tubules  of  the  first  order,  after  ramifying 
in  the  cortical  substance,  become  continuous  with  the  looped 
tubules  of  Henle,  as  already  described.2  The  change  takes 
place  in  the  vicinity  of  the  boundary  layer. 

The  looped  tubules. — The  looped  tubules  traverse  the 
medulla  for  a  greater  or  lesser  distance.  A  few  almost  reach 
the  apices  of  the  pyramids  ;  others  extend  but  a  short  distance 
below  the  boundary  layer,  while  a  third  class  occupies  an  inter- 
mediate position.  Good  specimens  are  obtained  by  macerating 
vertical  sections  of  the  medulla  in  a  solution  of  caustic  potassa 
(i  to  1  per  cent.).  The  potassa  destroys  the  epithelium,  the 
stroma,  and  the  blood-corpuscles,  but  leaves  the  basement- 

1  Resinous  turpentine  is  prepared  as  follows :  some  common  oil  of  turpentine  is 
poured  upon  a  deep  plate,  so  as  to  form  a  thin  layer,  and  a  piece  of  fine  muslin  is 
snugly  fastened  over  it  to  keep  out  the  dust.  The  liquid  is  now  exposed  to  the  ac- 
tion of  the  air.  In  a  few  days,  if  the  weather  be  warm,  or  a  week  or  more,  if  the 
weather  be  cold,  the  turpentine  will  have  become  thick,  yellow,  and  resinous,  and  is 
now  no  longer  transparent.  Resinous  turpentine,  prepared  in  this  way,  forms  one  of 
the  best  preserving  agents.  Its  use  will  be  spoken  of  further  on. 

-  Henle:  Eingeweidel.,  2te  Aufl.,  p.  316. 


210  MANUAL    OF   HISTOLOGY. 

membrane  perfectly  intact.  A  fresli  kidney  is  necessary,  and 
one  slightly  infiltrated  with  fat  makes  the  best  specimens. 
Another  method  is  to  embed  the  kidney  of  a  dog  or  rabbit 
in  powdered  chlorate  of  potassa,  adding  enough  dilute  nitric 
or  hydrochloric  acid  to  cover  the  crystals.  After  some  hours 
the  connective  tissue  in  the  gland  will  have  been  destroyed. 
Portions  of  the  medulla  should  then  be  placed  upon  a  slide 
with  a  drop  of  glycerine  and  teased  slightly.  A  great  many 
of  the  loops  are  broken  in  this  way,  to  be  sure,  but  still  some 
will  be  seen,  By  this  method  the  epithelium  of  the  narrow 
branch  is  not  destroyed. 

TJie  epithelium  of  the  looped  tubules. — The  descending 
branch  of  the  loop  is  small  in  diameter  (0.02  mm.)  and  pos- 
sesses a  peculiar  distinctive  epithelium.  The  corpuscles  are 
flat,  have  prominent  nuclei,  and  rest  against  the  membrana 
propria.  The  disproportionate  size  of  the  nuclei  causes  the 
corpuscle  to  project  into  the  lumen.  But  these  prominences 

do  not  obstruct  the  passage, 
for  each  one  corresponds  to 
the  space  between  two  on 

FIG.  96.— Kidney  of  dog.     Descending  portion  of       the  Opposite   side    of    tll6  tU- 
Henle's  looped  tubule.  ,       -,  i  -  -, 

bule,  so  that  there  is  no  bar 

to  the  urine,  but  the  passage  is  made  more  or  less  spiral  (Fig. 
96).  The  corpuscles  are  of  a  light  color.  Specimens  should 
be  made  from  a  gland  that  has  been  macerated  in  a  5  per  cent, 
solution  of  the  neutral  chromate  of  ammonia;  they  should 
be  examined  in  glycerine.  The  length  of  the  narrow  portion 
of  the  loop  is  variable  in  man,  the  pig,  and  horse. 

The  second  portion  of  the  looped  tubule  is  wider  and  its 
epithelium  peculiar.  In  man  both  the  loop  and  ascending 
branch  are  wide,  usually  ;  especially  is  this  the  case  with  loops 
high  up  in  the  medulla ;  in  the  rabbit  it  is  the  ascending 
branch  only  that  has  this  property.  Generally  speaking,  the 
length  of  the  broader  branch  of  the  loop  exceeds  that  of  the 
narrow  portion.  The  diameter  of  the  broad  portion  averages 
0.04  mm.  The  epithelium  has  the  same  character  as  that  in 
the  convoluted  tubules  ;  it  is  striated  and  possesses  rods.1  It 
is  not  precisely  similar,  however.  The  width  of  the  individual 
cells  is  not  so  great  as  in  the  former,  and  hence  the  lumen  in 


1  Heidenhain  :  loc.  cit.     Henle  :  loc.  cit. ,  p.  317. 


THE    KIDNEY.  211 

this  portion  of  the  loop  is  greater  than  in  the  convoluted  tu- 
bules. Specimens  prepared  with  the  neutral  chromate  of  am- 
monia, as  before  detailed,  give  good  results.  Vertical  sections 
may  be  made  from  a  kidney  macerated  in  the  ammonia  solu- 
tion and  afterward  treated  with  alcohol  ;  or,  better,  from  frozen 
specimens. 

The  broader  extremity  of  the  looped  tubule  ascends  through 
the  medulla  into  the  cortical  substance  and  becomes  continu- 
ous with  a  convoluted  tubule  of  the  second  order  (Fig.  91,  i). 
These  tubules,  the  intercalated  portions,1  greatly  resemble  con- 
voluted tubules  of  the  first  order,  as  already  mentioned.  Spe- 
cimens should  be  prepared  in  the  same  way  as  those  of  the 
latter.  The  convoluted  tubules  of  the  second  order,  after  rami- 
fying in  the  cortical  substance,  terminate  by  emptying  into  the 
collecting  tubules  (Fig.  91,  J). 

The  collecting  tubules  and  their  epithelium.  —  The  collecting 
tubules  a  possess  cylindrical  epithelia,  the  bases  of  which  are 
irregular  and  present  point-like  prolongations  3  (Fig.  97),  which 
interdigitate  with  one  another.  The  nuclei  in 
the  smaller  collecting  tubules  are  large  and 
very  prominent,  but  the  protoplasm  which  sur- 
rounds them  is  not  very  abundant.  The  base- 
ment membrane  is  comparatively  thick  and 
exhibits  a  double  contour.  The  smaller  col- 
lecting tubules  are  situated  in  the  cortical  sub- 
stance, a  little  distance  below  the  capsule. 

_,.  _  FIG.  97.—  Kidney  of 

Their  diameter  ranges  between  0.04  and  0.06    d°s-   isolated  ceiis  of 

0  two   collecting  tubnles, 

mm.     The  small  tubules  unite  to  form  larger    Bowing  irregular  base 

°  and  point-like  prolonga- 

ones,  and  these  again  to  form  tubules  of  still    jJJSiiS 


larger  diameter.  The  irregular  appearance  at  from  one^near  boundary 
the  bases  of  the  epithelia  is  the  same  in  the 
larger  trunks  as  in  the  smaller  branches  ;  in  the  former,  how- 
ever, the  cells  are  larger,  and  the  protoplasm  more  voluminous 
than  in  the  latter.  The  nuclei  have  about  the  same  size  in 
each  (Fig.  98).  The  basement-membrane  diminishes  in  impor- 
tance in  an  inverse  ratio  with  the  size  of  the  collecting  tubules. 
In  the  smaller  ones  it  is  prominent  and  possesses  a  double  con- 


1  Schweigger-Seidel :    Schaltstiicke ;    Roth  :   Verbindungscanale  (connecting  tu- 
bules). 

2  Open  tubules  of  Henle.     Zur  Anat.  der  Niere.     Gottingen,  1862. 

3  Heidenhain  :  loc.  cit. 


212 


MANUAL    OF    HISTOLOGY. 


tour ;  in  those  of  intermediate  size  it  is  thin,  and  has  but  a 
single  contour ;  the  largest  tubes  possess  no  basement-mem- 
brane whatever.  In  the  latter  the  great  cylindrical  cells  are 
held  together  by  the  prolongations  above  mentioned  and  a 
colloid  substance.  The  diameter  of -the  largest  tubules  at  the 
apices  of  the  pyramids  is  0.2  to  0.3  mm.,  after  the  first  division 
0.1  to  0.2  mm.,  the  smallest  being  about  0.06 
mm.  The  height  of  the  epithelium  in  the 
largest  tubules  is  between  0.02  and  0.04  mm.  ; 
in  those  at  the  boundary  layer  about  0.015 
mm.  Good  specimens  are  obtained  by  im- 
mersing a  fresh  gland  in  dilute  muriatic  or 
nitric  acid  for  a  variable  period  (six  to  twenty- 
four  hours),  and  examining  in  dilute  gly- 
cerine. The  collecting  tubules1  should  be 
injected  from  the  ureter  with  blue  or  red  gel- 
atine, and  the  whole  organ  immersed  in  alco- 
hol, until  ready  for  cutting.  Sections  made 
parallel  to  the  collecting  tubules  produce  t 
splendid  specimens.  The  connection  between 
the  collecting  and  convoluted  tubules  of  the 
human  kidney  cannot  be  shown  by  injection, 
for  the  colored  fluid  thrown  in  from  the  ure- 
ter rarely  reaches  the  convoluted  tubules  of  the  first  order.  In 
the  lower  animals — fishes,  frogs,  etc. — however,  if  the  ureter  be 
injected  under  constant  pressure  the  entire  length  of  the  urin- 
iferous  tubules  may  be  filled  with  the  carmine,  or,  better,  Berlin 
blue2  fluid. 


FIG.  98. —Kidney  of 
dog.  Small  collecting  tu- 
bule above  the  boundary 
layer,  x  450. 


1  In  the  pig  Henle  finds  that  two  large  collecting  tubules  begin  at  the  apex  of 
each  pyramid,  then  run  along  the  outer  borders  of  the  cortical  substance  proper, 
high  up  into  the  cortex,  and  there  unite  by  forming  a  loop.  Henle  states  that 
the  convoluted  tubules  empty  into  these,  or  their  divisions  by  intercalated  portions, 
which  he  calls  communicating  tubules  ( Vcrbindungscanalcheri).  Eingeweidel. ,  p.  324. 

9  This  has  been  done  by  Frey  with  fishes  and  amphibia ;  by  Hiifner  with  birds, 
fishes,  etc.  ;  by  Gross  with  fishes  and  tritons,  and  by  Hyrtl  with  some  sorts  of  fishes. 
According  to  Seraphina  Schachowa  (Unters.  ueber  die  Niere.  Diss.  Bern,  1 870)  the 
convoluted  tubule  of  the  first  order  is  connected  to  Henle' s  loop  by  a  spiral  tubule, 
while  the  ascending  portion  of  the  loop  exhibits  an  expanded  part  immediately  above 
the  loop,  and  a  spiral  part,  which  latter  becomes  continuous  with  the  ascending  limb 
of  the  loop.  Between  the  ascending  part  of  the  loop  and  the  intercalated  portion 
Schachowa  describes  a  new  tubule,  which  she  calls  the  "  irregular  tubule." 

The  spiral  tubule  is  lined  with  an  epithelium  which  has  a  striated  appearance  in 


THE    KIDNEY. 


213 


The  Hood-vessels  of  tlie  kidney. — The  renal  artery  and  vein, 
before  entering  the  hilum,  divide  and  subdivide  within  the 
sinus  of  the  kidney.  Small  branches,  which  are  given  off  at 
the  hilum,  also  supply  the  fibrous  capsule  of  the  gland.  Veins 
accompany  the  arteries  as  far  as  the  arches  already  referred  to. 
But  here  a  difference  is  to  be  noted.  The  arteries  never  anas- 
tomose, but  form  the  straight  vessels  of  the  cortical  substance 
proper,  which  again  send  off  twigs  to  form  the  glomeruli. 


FIG.  99. — Kidney  of  pig.  Injection  of  artery  and  vein.  Vertical  section  at  boundary  layer :  A, 
artery ;  B,  vein  :  C,  glornerulus ;  D,  capillaries  of  the  cortical  portion ;  E,  vasa  recta  formed  from 
capillaries  D.  x  96. 

At  the  arches,  however,  the  veins  anastomose,  and  a  branch 
accompanies  the  straight  artery  of  the  cortical  substance  proper 
(Fig.  99,  B).  The  glomerulus  is  formed  from  the  arterial  twig 
above  referred  to  (Fig.  89,  D).  This  enters  the  capsule  directly 
opposite  to  the  point  where  the  latter  becomes  continuous 
with  a  convoluted  tubule,  and  divides  into  two  or  more 


its  first  portion.  The  expanded  part  of  the  ascending  loop  is  lined  with  cells  having 
very  thick  prominent  rods,  and  whose  lumen  is  exceedingly  small.  ' 

The  irregular  tubule  has  an  angular,  irregular  outline,  is  of  very  varying  diameter, 
in  some  portions  two,  three,  or  four  times  as  broad  as  in  other  portions,  a  condition 
due  to  its  peculiar  lining  epithelia,  which  are  angular  and  present  numerous  pro- 
the  rods  are  exceedingly  thick  and  prominent. 

As  yet  I  have  been  unable  to  confirm  Schachowa's  researches. 


214  MANUAL    OF    HISTOLOGY. 

branches  which  subdivide  again  and  again  (Fig.  100)  to  form 
loops  or  coils  ;  these  latter  unite  again  and  form  a  vessel  equal 
in  size  to  the  one  which  entered  the  capsule.  The  first  is 

called,  as  already  described,  the  affer- 
ent ;  the  second,  the  efferent  vessel, 
and  the  glomerulus  is  formed  by  the 
division  and  reunion  of  the  branches 
of  these  two  vessels ;  the  whole  form- 
ing a  rounded  tuft  within  the  capsule. 
The  vessels  of  which  a  glomerulus  is 
composed  have  the  same  diameter  as 
FIG.  loo.— Giomeruius  from  kidney  small  capillaries  i  their  coats  are  struc- 

of  pig.    Ludwig.  '    .  .  . 

tureless  and  provided  with  elliptical 

nuclei.  The  efferent  vessels  are  not  veins  ;  on  leaving  the  cap- 
sules they  break  up  into  capillaries,  which  anastomose  freely 
with  each  other  and  surround  the  tubules  of  the  cortex,  form- 
ing, in  this  way,  a  network  with  circular  meshes  (Fig.  99,  D). 

At  the  boundary  layer  the  capillaries  unite  to  form  vessels 
which  are  two  to  three  times  larger  than  the  original  capillaries. 
These  vessels  take  a  straight  course  through  the  medulla  to- 
ward the  apices  forming  the  so-called  vasa  recta '  (Figs.  99,  E, 
and  89,  G).  The  vessels  immediately  below  the  boundary  layer 
are  arranged  in  bundles  at  the  side  of  the  pyramidal  prolonga- 
tions, and  run  parallel  with  them  in  that  part  of  the  medulla 
(Fig.  89).  They  give  off  branches  in  the  medulla,  and  near  the 
apices  of  the  pyramids  again  form  a  capillary  network  which 
surrounds  the  collecting  tubules.  The  returning  vessels  (veins) 
have  about  the  same  course,  anastomose  freely  with  each  other, 
and  empty  into  the  venous  arches  at  the  boundary  layer. 
Other  veins  are  formed  by  the  union  of  capillaries  immediately 
underneath  the  capsule  ;  these  have  a  stellate  form,3  the  centre 
of  each  star  indicating  the  commencement  of  a  vein.  Such 
veins,  passing  downward  through  the  cortex  and  receiving 
branches  on  the  way,  empty  finally  into  the  venous  arches 
above  referred  to.  The  venous  arches  also  give  rise  to  vessels 
of  larger  calibre,  which  run  parallel  to  and  accompany  the  ar- 
teries of  the  medulla,  and  at  last  unite  to  form  the  renal  vein. 

Injections  of  the  kidney.  —The  kidney  may  be  injected  with 
gelatine  either  through  the  artery  or  vein.  It  is  best  accom- 

1  Bonders:  Physiol.,  L  2  Venae  Stettatce,  Verheyen. 


THE   KIDNEY.  215 

plished  by  the  artery,  under  constant  pressure  (mercury). 
Beale's  blue  injecting  fluid l  answers  very  well ;  the  writer's  car- 
mine-glycerine fluid3  also  acts  exceedingly  well,  but  it  is  very 
difficult  to  obtain  a  good  double  injection  of  artery  and  vein. 
I  have  found  the  most  successful  method  to  be  the  following  : 
Take  a  fresh  bloodless  kidney  (dog,  pig)  and  inject  the  vein 
under  constant  pressure  with  the  blue  gelatine  mass.3  Next 
place  the  kidney  in  iced  water  for  a  few  minutes  to  harden  the 
gelatine,  and  then  attach  to  the  artery  a  very  small  constant- 
pressure  injecting  apparatus,  the  receptacle  for  the  injecting 
fluid  containing  the  writer' s  carmine  fluid.  After  regulating  the 
amount  of  pressure,  the  whole  apparatus,  with  the  kidney,  is 
placed  within  the  receiver  of  an  air-pump  and  the  air  slowly 
exhausted.  In  this  way  the  arteries  become  filled  with  fluid. 
Allow  the  gland  to  harden  in  alcohol  and  mount  the  sections 
in  balsam  or  dammar.  Kidneys  in  which  the  vein  and  artery 
have  been  injected  may  have  the  collecting  tubules  filled  from 
the  ureter  with  yellow  injecting  fluid,  thus  making  a  triple 
injection.  Sections  of  kidney  hardened  in  alcohol  may  be 
stained  with  borax- carmine,  and  afterward  bleached  in  a  di- 
lute hydrochloric  acid  (1  to  10)  solution,  or  a  concentrated  one 
of  oxalic  acid.  When  the  vessels  of  a  kidney  have  been  injected 
with  blue  gelatine,  staining  with  carmine  gives  good  results. 

Thiersch's  yellow  injecting  fluid  is  made  as  follows  :  Prepare  a  solution  of 
bichromate  of  potassa,  one  part  of  the  salt  to  eleven  parts  of  water,  and  a  solu- 
tion of  nitrate  of  lead  of  the  same  strength.  One  part  of  the  potassa  solution 
is  placed  in  a  small  basin  and  mixed  with  four  parts  of  a  concentrated  solution 
of  gelatine.  Two  parts  of  the  lead  solution  are  placed  in  another  basin  and 
mixed  with  four  parts  of  jelly.  These  are  to  be  slowly  and  thoroughly  mixed 
together  at  a  temperature  of  75°  to  90°,  and  then  heated  in  a  water-bath  at  a 
temperature  of  212°  for  half  an  hour  or  more.  Filter  carefully  through  flannel 
(Beale  :  Microscope,  p.  90). 

The  kidney  stroma. — In  the  cortical  substance  the  stroma 
is  reduced  to  a  colloid  material  which  binds  the  tubules  to- 
gether. In  the  lower  part  of  the  medulla,  in  the  fresh  state, 

1  See  page  205. 

*  Carmine,  5  grammes;  glycerine  (anhydrous),  50 grammes;  add  caustic  potassa 
until  the  carmine  is  dissolved,  and  neutralize  with  pure,  concentrated  muriatic  acid. 

3  Gelatine  should  be  first  immersed  in  water  until  it  becomes  softened  and  then 
gently  heated  until  dissolved.  Add  soluble  Berlin  blue,  or  Beale's  blue  fluid,  until  a 
good  color  is  obtained.  Inject  while  hot. 


216  MANUAL    OF   HISTOLOGY. 

the  stroma  is  a  colorless,  transparent  substance,  which,  after 
immersion  for  a  variable  time  in  a  solution  of  euro  mate  of  po- 
tassa  or  ammonia,  resolves  itself  into  a  thin  fibrous  reticulum, 
containing  at  regular  intervals  round  or  elliptical  nuclei ;  * 
these,  according  to  Schweigger-Seidel,  belong  to  stellate  or 
spindle-shaped  corpuscles,  which  may  be  isolated  by  macera- 
tion in  hydrochloric  acid.  The  nuclei  are  only  seen  in  the 
lower  portion  of  the  medulla  ;  the  fibrous  appearance  of  the 
stroma  is  retained  some  distance  beyond  this  point. 

The  nerves  follow  the  course  of  the  arteries  of  the  kidney 
and  seem  to  supply  only  those  vessels. 

The  lymphatics  at  the  hilum  are  derived  from  the  interior 
of  the  organ,  and  from  a  network  of  small  lymph-branches 
situated  between  the  bundles  of  fibres  of  the  capsule.  The 
latter  communicate  with  lymph-canals  in  the  interior  of  the 
organ.2 

The  capsule  of  the  kidney  is  a  fibrous  tissue,  containing 
some  few  elastic  filaments.  It  is  divisible  into  two  layers,  an 
outer  and  an  inner  one.  The  former,  about  0.1  to  0.2  mm.  in 
thickness  is  continuous  with  the  connective  tissue  which  sur- 
rounds the  blood-vessels  at  the  hilum  ;  the  latter,  about  0.025 
mm.  in  thickness,  terminates  at  the  points  where  the  papillae 
enter  the  calices.  Immediately  underneath  the  inner  layer,  is 
a  large  meshed  reticulum  of  smooth  muscle-fibres,3  some  of 
which  traverse  the  substance  of  the  gland  for  a  short  distance. 

The  calyx,  at  its  junction  with  the  papilla,  is  covered  with 
epithelium,  which  is  continued  on  to  the  apex  of  the  papilla  ; 
it  contains,  in  addition,  muscle-fibres  disposed  at  right  angles 
to  one  another,  and  connective  tissue. 

Natural  injection  of  the  tubules  of  the  ~kidney  by  the 
sulphindigate  of  soda.* — The  first  to  inject  the  kidney  in  this 
way  was  Ghronsczewski ; 6  but  his  experiments  were  not  very 
successful,  at  least  so  far  as  the  kidney  was  concerned.  Those 
of  Heidenhain 6  which  have  been  confirmed  by  the  writer,7  give 


1  Henle  :  loc.  cit.  2  Ludwig,  in  Strieker's  Manual. 

3  Eberth :  Med.  Centralbl.,  No.  15,  1872. 

4  Commonly  known  in  the  laboratory  and  in  commerce  as  indigo-carmine. 

5  Chronsczewski,  in  Virchow's  Archiv,  Bd.  XXXI.,  p.  187;   also  Bd.  XXXV.,  p. 
158. 

6  Max  Schultze's  Archiv,  Bd.  X.,  p.  1,  and  Pfliiger's  Archiv,  Bd.  IX.,  p.  1. 

7  Mayer  ;  Histol.  of  Kidney.     Prize  dissert. ,  1876. 


THE    KIDNEY.  217 

the  most  satisfactory  results.     To  insure  this  desirable  end,  it 
is  necessary  that  the  sulphindigate  of  soda  be  pure. 

O.  Maschke,  of  Breslau,  the  apothecary  who  manufactures  the  pure  sulphin- 
digate of  soda  for  Prof.  Heidenhain,  writes  to  that  author  as  follows  :  "  The 
indigo- sulphate  of  soda  was  prepared  from  the  phoanicin-sulphate  of  soda.  If 
the  latter  compound  be  heated  for  half  to  one  hour,  at  a  temperature  of  60°  to 
70°  C.,  with  five  or  six  times  its  volume  of  sulphuric  acid  of  a  specific  gravity 
of  1,840,  it  resolves  itself  completely  into  indigo- disulphate  of  soda  and 
indigo-monosulphate  of  soda  (indigunterschwefelsaures  Natron).  I  have 
chosen  this  mode  of  preparing  the  salt  because  the  indigo-gelatine  and  indigo- 
brown  can  easily  be  separated  from  the  phoenicin-sulphate  of  soda,  without 
marked  loss,  and  in  this  way  I  obtain  a  sufficiently  pure  substance  for  future 
use.  An  easier  method  of  preparing  the  salt  is  the  formula  given  by  Crum 
and  Berzelius.  One  part  of  best  indigo  in  powder  is  gradually  added  to  seven 
or  eight  parts  of  pure  sulphuric  acid,  specific  gravity  1,84=0,  in  a  large  vessel, 
and  the  two  thoroughly  mixed.  After  the  liquid  has  ceased  to  froth,  the 
Vessel  is  covered  with  an  animal  membrane  and  put  aside  for  three  days,  during 
which  interval  it  is  to  be  frequently  shaken.  To  this  solution  thirty  to  forty 
volumes  of  water  are  added,  and  the  whole  carefully  filtered.  To  the  resulting 
clear  solution  as  many  parts  by  weight  of  crystallized  carbonate  of  soda  as 
there  were  of  sulphuric  acid,  are  added.  Owing  to  the  effervescence  which 
now  takes  place,  the  vessel  in  which  the  mixture  is  prepared  must  be  of  large 
size.  For  this  reason  it  is  better  to  substitute  the  acetate  of  soda,  or  chloride 
of  sodium,  or  simply  sulphate  of  soda,  for  the  formation  and  precipitation  of 
the  indigo-disulphate  of  soda  takes  place  with  any  soda  salt  which  does  not 
decompose  the  "indigo -disulphuric  acid.  The  mixture  is  now  filtered,  and  the 
precipitate  dried  over  a  water-bath.  It  is  then  pulverized  and  treated  re- 
peatedly with  absolute  alcohol,  which  dissolves  any  indigo-monosulphate  of 
soda,  acetate  of  soda,  or  indigo-red,  which  may  have  remained."  In  this  way 
the  indigo-carmine  is  obtained  in  a  pure  state.  The  crystals  are  copper-colored, 
but  the  salt  is  blue  in  the  pulverized  state.  The  indigo-carmine  of  commerce 
is  an  impure  article  and  cannot  be  used  for  natural  injection. 

For  injection,  a  cold  saturated  solution  of  the  sulphindigate 
of  soda  is  used  ;  the  salt  may  be  dissolved  in  boiling  distilled 
water,  and  the  solution  allowed  to  cool.  A  dog  or  rabbit 
answers  for  the  purpose  of  injecting.  The  animal  is  properly 
fastened  to  a  board,  and  the  external  or  internal  jugular  vein 
dissected  up  and  exposed.  In  either  of  these  vessels  a  canula 
with  stop-cock,  previously  filled  with  the  indigo-carmine 
solution,  is  inserted.  The  injection  into  the  jugular  may  be 
made  downward  or  upward — the  latter  is  preferable.  A  syr- 
inge, graduated  in  cubic  centimetres  and  containing  the  sol- 
ution of  indigo-carmine,  is  now  attached  to  the  canula,  the 
stop-cock  opened  and  a  small  quantity  of  the  solution  injected 


218  MANUAL    OF    HISTOLOGY. 

into  the  vein.  Not  more  than  5  c.c.  should  be  injected  at  one 
time.  If  the  animal  be  a  white  rabbit,  the  result  oi!  the  first 
injection  shows  itself  in  a  few  seconds,  for  the  animal  soon 
becomes  quite  blue.  After  five  or  ten  minutes  another  5  c.c. 
of  the  solution  may  be  injected,  and  so  on  until  20  to  50  c.c.  of 
indigo-carmine  solution  have  been  employed,  the  amount 
varying  according  to  the  size  of  the  animal. 

The  excretion  of  blue  urine  takes  place  soon  after  the  first 
injection  of  indigo-carmine.  As  soon  as  a  sufficient  quantity 
has  been  excreted  the  animal  is  killed  in  the  following  manner  : 
The  abdomen  is  opened  and  the  descending  aorta  looked  for  ; 
when  found,  the  canula  of  a  syringe,  filled  with  absolute  alcohol, 
is  attached.  The  jugular  vein  is  now  cut  across,  and  while 
the  animal  bleeds  to  death  absolute  alcohol  is  injected  up  the 
aorta  or  into  the  renal  arteries.  A  safer  and  better  way  is  to 
inject  the  renal  artery  at  once  with  absolute  alcohol ;  in  either 
case  the  renal  veins  should  be  cut  across.  The  kidney  is  at 
once  removed,  placed  in  absolute  alcohol,  and  then  divided 
into  several  pieces,  to  insure  a  rapid  action  of  the  spirit. 
While  the  indigo -car  mine  is  being  injected  into  the  jugular 
vein,  the  animal  should  be  wrapped  up  in  flannel  or  cotton- 
batting  so  as  to  be  kept  warm.  No  air  should  be  allowed  to 
enter  the  vein,  or  the  animal  may  die  before  the  experiment  is 
concluded.  Injection  of  absolute  alcohol  through  the  renal 
artery  should  be  accomplished  before  the  animal  has  bled  to 
death,  or,  at  least,  immediately  afterward.  When  the  kidney 
has  been  thoroughly  hardened,  vertical  and  transverse  sections 
are  to  be  made  through  the  cortical  and  medullary  substances, 
and  examined  in  glycerine  saturated  in  chloride  of  potassium  ; 
or,  better  still,  in  resinous  turpentine. 

If  the  injection  of  absolute  alcohol  be  delayed,  either  through  lack  of  skill  in 
the  experimenter,  or  any  mishap,  the  indigo  salt  within  the  kidney  becomes 
diffused  over  the  entire  organ  by  absorption  of  water  from  the  contained  ves- 
sels, and  the  whole  kidney  becomes  of  a  uniform  blue  color.  Such  glands 
must  be  laid  aside,  for  sections  made  therefrom,  even  after  immersion  in  abso- 
lute alcohol,  are  worthless,  and  will  only  confuse  the  microscopist.  The  abso- 
lute alcohol  of  the  shops  is  not  always  absolute,  as  is  well  known.  It  has  a 
great  affinity  for  water,  and,  in  handling,  rapidly  absorbs  moisture  from  the  air. 
To  make  it  absolute,  I  heat  sulphate  of  copper  (pure)  at  a  low  red-heat.  This 
drives  out  the  water  of  crystallization,  and  changes  the  color  from  blue  to 
white.  Of  this  I  mix  a  large  spoonful  or  more,  while  still  hot,  with  a  pint  of 
the  so-called  absolute  alcohol,  and  tightly  cork  the  vessel,  which  is  then  to  be 


THE    KIDNEY.  219 

shaken  occasionally,  but  not  used  for  a  week  or  more.  The  affinity  that  water 
has  for  anhydrous  sulphate  of  copper  is  greater  than  that  of  the  alcohol,  and 
the  latter  readily  gives  it  up.  As  soon  as  the  anhydrous  sulphate  regains  its 
water  of  crystallization  it  assumes  a  blue  color  again. 

Everywhere  in  the  sections  it  will  be  seen  that  the  glomeruli 
or  their  capsules  are  entirely  free  from  color,  while  all  the 
tubules  possessing  the  rod-epithelium  have  a  more  or  less  blue 
color,  according  to  the  quantity  of  indigo-carmine  excreted. 
The  lumina  of  the  convoluted  and  other  tubules  are  generally 
filled  with  the  crystallized  indigo-salt.  In  examining  sections, 
it  soon  becomes  evident  that  the  convoluted  tubules  and  that 
part  of  Henle's  loop  which  possesses  the  rod-epithelium,  alone 
excrete  the  indigo-salt,  while  the  other  tubules  merely  contain 
it  in  their  lumen,  the  salt  having  been  washed  down,  as  it  were, 
from  above  by  the  water  filtered  through  the  capillaries  of  the 
glomeruli. 

Instead  of  using  the  sulphindigate  of  soda,  Heidenhain,  in  his  second  series 
of  experiments,  substituted  a  solution  of  uric  acid  in  caustic  soda.  The  renal 
artery  was  injected  with  alcohol  containing  acetic  acid.  The  result  showed 
that  urate  of  soda,  like  the  indigo-salt,  was  excreted  only  by  the  tubules  pos- 
sessing the  rod- epithelium.  The  capsules  were  entirely  free.  The  addition  of 
acetic  acid  to  the  alcohol  caused  the  uric  acid  to  be  precipitated  in  the  shape 
of  rhomboid  crystals  within  the  tubules.  In  this  condition  Heidenhain  found 
them.  The  hypothesis  set  down  by  Bowman,  years  ago,  that  the  tubules  of 
the  kidney  excrete  the  solid  constituents  of  the  urine  merely,  while  the  glome- 
ruli serve  as  a  filter  for  the  fluid  portion,  is  therefore  correct. 

If  the  quantity  of  indigo  solution  injected  into  the  jugular 
be  small,  and  the  animal  killed  soon  after,  the  kidney  being 
treated  as  above  detailed,  the  microscopic  sections  exhibit 
the  following  appearance :  glomerulus  and  capsule  are  not 
acted  upon  ;  the  narrower  branch  of  the  loop  and  the  collect- 
ing tubules  are  free  from  any  crystallized  salt,  and  their  epi- 
thelium clear.  In  the  convoluted  tubules  and  the  broad  part 
of  the  loop,  the  following  phenomena  may  also  be  observed : 
their  lumina  are  entirely  free  from  any  deposit  of  indigo-car- 
mine, though  here  and  there  the  rod-epithelium  is  not  stained. 
In  the  greater  number  it  is  colored  of  a  light  blue  color.  In  some 
the  rods  and  nuclei  are  uniformly  stained  ;  in  others  the  rods 
alone  show  the  blue  color,  while  the  nuclei  are  not  stained. 
This  constitutes  the  first  stage  of  the  excretion  of  indigo-car- 


220 


MANUAL    OF    HISTOLOGY. 


mine  through  the  kidneys.  If  a  larger  quantity  of  indigo 
solution  be  injected,  and  the  animal  dealt  with  as  above,  the 
second  stage  of  the  excretion  is  seen.  Here,  again,  the  glome- 
ruli,  the  capsules,  and  the  collecting-tubules  are  free  from 
color,  the  rod-epithelium  stained  blue,  and  their  nuclei  dark 
blue  (Fig.  101,  F).  In  a  few  of  the  convoluted  tubules  and  the 
ascending  broad  branches  of  the  loop,  crystals  of  indigo-salt 


PiG.101. — Kidney  of  dog.  Natural  injection  of  secreting  portion,  artificial  injection  of  artery,  vein, 
and  capillaries.  Transverse  section  through  cortical  substance  :  A,  afferent  vessel,  filled  with  injected 
material;  B,  efferent  vessel,  also  filled  with  injection;  E,  glomerulus,  injected  and  Ijing  within  its  cap- 
sule :  epithelium  of  latter  distinctly  seen :  D,  capillaries  surrounding  the  convoluted  tubules,  and  dis- 
tended with  the  injection ;  at  this  point  four  capillaries  are  seen  to  unite  and  form  a  vein ;  C,  convo- 
luted tubule,  filled  with  crystals  of  indigo-carmine ;  F,  convoluted  tubule,  in  which  the  nuclei  have  a 
dark  color.  The  striations  of  Heidenhain  are  beautifully  shown  in  the  convoluted  tubules,  x  200. 


fill  the  lumina.  So,  also,  in  some  of  the  descending  narrow 
branches  of  the  loop.  In  the  third  stage  the  rods  are  color- 
less, while  their  nuclei  are  still  blue.  Masses  of  the  indigo - 
salt  fill  the  lumina  of  the  convoluted,  looped,  and  collecting 
tubules ;  the  glomeruli  and  their  capsules  are  colorless.  In 
the  last  stage,  the  salt  is  contained  in  the  lumina  of  the  col- 
lecting tubules  only,  all  the  rest  of  the  gland  being  free  from 
it,  and  consequently  colorless.  From  the  above  it  will  be 


THE    KIDNEY.  221 

seen  that  the  rod -epithelium  alone  excretes  the  indigo-salt,  and 
it  may  be  presumed,  therefore,  that  the  function  of  the  glome- 
ruli  is  to  act  as  a  filter  for  the  fluid  portion  of  the  urine.  Thus 
the  salt  is  washed  from  the  convoluted  into  the  collecting 
tubules,  and  thence  into  the  pelvis  of  the  kidney.  The  action 
of  absolute  alcohol  on  a  solution  of  sulphindigate  of  soda  is  to 
precipitate  that  salt.  It  is  this  action  within  the  kidney  which 
fixes'  the  dye,  as  above  set  forth. 

Beautiful  specimens  may  also  be  obtained  by  various  modi- 
fications of  the  above  process. 

The  following  formulae  and  results  are  given  by  Heidenhain : 

1.  Babbit  or  dog ;  section  of  spinal  cord,  injection  of  only  5  c.c.  of  the  in- 
digo solution,  the  animal  being  killed  after  ten  minutes.     Result :  pyramidal 
portion  and  boundary  layer  free  from  indigo-blue.     In  the  cortical  substance, 
some  of  the  convoluted  tubules  are  filled  with  the  crystalline  salt ;  in  the 
greater  number  the  epithelium  is  colored  of  a  uniform  blue,  the  nuclei  possess- 
ing the  same  tint ;  the  lumen  is  usually  free. 

2.  Same  conditions  as  above,  excepting  that  20  or  25  c.c.  of  the  solution 
is  injected.   Medulla  free  from  indigo  blue.   In  the  cortex  a  great  many  of  the 
tubules  are  filled  with  the  pigment,  while  the  epithelium  is  stained  blue,  the 
nuclei  of  a  deep  blue  color. 

3.  Same  conditions  as  in  2,  excepting  that  the  animal  is  killed  one  hour 
after  injection.     Nuclei  of  the  rod-epithelium  stained  deep  blue,  rods  clear ; 
convoluted  and  collecting  tubules  filled  with  crystals  of  pigment. 

Instead  of  using  absolute  alcohol  for  injecting  the  renal 
artery,  the  writer's  carmine-glycerine  fluid  may  be  employed. 
After  having  injected  the  artery  in  this  way,  the  kidney  is 
placed  in  a  vessel  of  absolute  alcohol,  and  divided  into  small 
pieces  while  immersed  in  that  fluid.  The  glycerine  being  anhy- 
drous, prevents  the  diffusion  of  the  indigo-salt  within  the  kid- 
ney, while  the  alcohol  fixes  the  pigment.  Sections  should  be 
made  from  the  cortex  and  medulla,  and  mounted  permanently 
in  resinous  turpentine.  If  the  glycerine  injection  has  been  suc- 
cessful, all  the  glomeruli  and  capillaries  will  be  filled  with  a 
transparent  red  mass  (Fig.  101).  If  the  indigo  excretion  has 
reached  the  third  stage,  the  collecting  tubules  in  the  medulla 
will  be  filled  with  blue  crystals  of  indigo-carmine,  and  the  vasa 
recta  with  a  red  mass,  the  two  arranged  in  alternate  rows. 
Such  specimens  leave  nothing  to  be  desired  in  the  way  of 
demonstrating  the  structural  relations  just  described. 


222  MANUAL    OF   HISTOLOGY. 


BIBLIOGRAPHY. 

FERREIN.     Mem.  del'acad.,  p.  502.     Paris,  1753. 

MULLER.     De  glandularum,  etc.     Leipz.,  1830.     And  Unters.  lib.  d.  Eingew.    d. 

Fische.     Berlin,  1845. 

HUSCHKE.     Lehre  d.  Eingeweide.     Leipz.,  1844. 
GERLACH.     Miiller's  Archlv,  p.  378,  1845,  and  p.  102,  1848. 
VIRCHOW.     Virchow's  Archiv.     Bd.  XII.,  p.  310.     1857. 
BEER.     Die  Bindesubstanz  d.  Niere,  etc.     Berlin,  1859. 

LUDWIG.     Handb.  d.  Phys.     Bd.  II.,  p.  628.     And  Wiener  med.  Wochen.     1864. 
ROTH.     Diss.     Bern,  1864. 

CHRONSCZEWSKI.     Virchow's  Archiv.     Bd.  XXXI. ,  p.  153.     1864. 
SCHWEIGGER-SEIDEL.     Die  Niere,  etc.     Halle,  1865. 
STILLING.     Bin  Beitrag,  etc. ,  Diss.    Marburg,  1865. 
HUFNER.     Vergl.  Anat.  u.  Phys.  d.  Harn.     Leipz.,  1866. 
LINDGREN.     Z.  f.  rat.  Med.     1868. 

GROSS.     Essai  sur  la  structure  microscopique  des  reins.     Strassbourg,  1868. 
ISAACS.    Jour,  de  la  phys.     Tome.  I.,  p.  577.     1858. 
LUDWIG.     Strieker's  Manual.     1871. 
EBERTH.     Centralb.  f.  d.  med.  Wiss.,  p.  227.     1872. 
HENLE.     Eingeweidel.,  2  Aufl.     1874. 

FREY.     Mikroskop.     6  Aufl.     1877.     And  Handb.    4  Aufl.     1874. 
HEIDENHAIN.     Schultze's  Archiv.     Bd.  X.     1874.     And  Pfluger's  Arch.     Bd.  IX. 

1874. 

SCHACHOWA.     Unters.  lib.  d.  Niere.    Diss.     Bern,  1876. 
NUSSBAUM.     Beitr.  z.  Anat.  und  Phys.  d.  Niere  Sitzungsber.  d.  Niederrh.  u.  Sw. 

Bonn,  1877. 

RUNEBERG.     Nord.  Med.    Ark.   XI.,  2.     No.  13.     1879. 
HENSCHEN.     Akad.  Afhandling  in  Upsula.     Stockholm,  1879. 
KLEIN  and  SMITH.     Atlas  of  Histology.     Part  XI.     1880. 


CHAPTER  XV. 

THE  MALE  EXTERNAL  AND  INTERNAL  OEGANS  OF  GENERATION, 
WITH  THEIR  GLANDULAR  APPENDAGES. 

BY  DR.  J.  HENRY  C.  SIMES, 
Lecturer  on  Histology,  University  of  Pennsylvania. 

Penis. — The  copulative  organ  of  the  male  consists  of  erec- 
tile tissue,  and  is  made  up  of  three  bodies,  each  enclosed  in  a 
fibrous  membrane,  the  tunica  albuginea.  Two  of  these  bodies 
are  termed  corpora  cavernosa;  the  third  corpus  spongiosum ; 
through  the  latter  the  urethra  passes. 

The  tunica  albuginea  consists  of  connective  tissue  and  elas- 
tic fibres,  with  some  smooth  muscular  elements.  From  the  in- 
ternal surface  of  this  membrane  arise  numerous  trabeculaa,  or 
bands,  composed  of  the  same  tissue  as  the  membrane ;  they 
divide  and  subdivide,  forming  a  very  intricate  reticulum.  The 
cavities  thus  formed  freely  communicate  one  with  the  other, 
and  are  lined  with  a  single  layer  of  flattened  endothelial  plates. 
This  system  of  intercommunicating  lacunse  is  in  reality  nothing 
but  a  true  venous  network.  It  is  in  direct  communication  with 
the  veins  of  the  organ.  By  the  overfilling  of  these  cavities  with 
blood  the  erectile  state  is  produced. 

Externally,  the  tunica  albuginea  is  surrounded  by  loose 
subcutaneous  tissue,  in  which  numerous  elastic  fibres  are  pres- 
ent. Longitudinal  bundles  and  a  few  oblique  fibres  of  involun- 
tary muscle  are  also  found  in  this  areolar  tissue.  The  skin  cov- 
ering the  penis  is  thin,  and  possesses  numerous  fine  hairs, 
which  have  an  increased  length  as  the  root  of  the  organ  is 
approached ;  they  are  connected  with  ordinary  sebaceous 
glands  which  open  into  their  follicles.  Sudorific  glands  are 
also  present  in  the  skin  of  this  organ.  The  internal  leaf  of 
the  prepuce  resembles  closely  a  mucous  membrane ;  papillae 
are  numerous, -but  there  is  an  absence  of  hairs,  and  the  seba- 


224 


MANUAL    OF    HISTOLOGY. 


ceous  follicles  (Tyson's  glands)  are  sometimes  difficult  to  find 
in  the  adult.  In  new-born  children,  however,  these  glands  are 
abundant  and  well  developed.  The  convoluted  glands  are  here 
absent. 

The  extremity  of  the  penis  terminates  in  a  cone-shaped 
body,  the  glans  penis,  which  has  a  cavernous  structure  very 
similar  to  that  in  the  body  of  the  organ,  and  differing  only 

in  the  size  of  the  meshes  and 
the  trabeculse,  the  former  being 
smaller  and  the  latter  more  deli- 
cate. The  external  or  mucous 
surface  of  the  glans  is  covered 
with  a  laminated  pavement  epi- 
thelium, the  cells  of  the  upper 
layer  being  quite  flat,  those  of 
the  middle  layer  ribbed,  while  in 
the  lowest  l#yer  they  are  colum- 
nar. There  are  numerous  elastic 
fibres  in  the  mucous  membrane 
of  the  glans,  and  many  single 
or  branched  papillae  are  seen, 
some  containing  club  -  shaped 
nerve-terminations. 

The  system  of  blood-vessels 
in  connection  with  the  penis  con- 
sists of  arteries,  veins,  capilla- 
ries, and  cavernous  spaces.  The 
modes  of  communication  between 

these  several  vascular  structures 

FIG.  m-Transverse  section  through  the  in-  are  three:  a  direct  passing  of  the 

jected  glans :   a,  epithelium  of  the  urethra  ?    &»  i  -i         -«      H               ±11                                 '    1   4- 

tunica  mucos«a;  c,  corpus  cavernoRum  urethrae ;  blOOU     IrOm  til 6  larger  ai'tei'ial  lO 

d,  corpus  cavernosum  glandis ;  e,  mucous  mem-  ,           ,                                             i                -U 

brane  of  the  glans  ;/,  epithelium  of  the  glans.  the      larger    VeUOUS      DranClieS  I     a 

Klein. 

somewhat  coarse  venous  reticu- 

lum  communicating  with  a  system  of  arterioles ;  and,  finally, 
a  direct  capillary  anastomosis. 

The  lymphatic  system  of  the  penis  is  represented  by  lymph- 
spaces,  capillaries,  and  large  trunks.  The  former,  the  spaces, 
are  oblong  in  shape,  and  occur  in  the  loose  subcutaneous  tissue 
surrounding  the  tunica  albuginea ;  they  communicate  with  a 
capillary  system,  which  is  disposed  in  longitudinal  meshes. 
The  large  lymph- trunks  formed  from  these  smaller  vessels  are 


THE  MALE  OKGANS  OF  GENERATION.         225 

situated  along  the  dorsum  of  the  organ,  and  communicate  with 
the  lymph-glands  in  the  pelvis  and  those  of  the  groin. 

The  nerves  and  their  terminations  in  the  penis  are  derived 
from  the  cerebro- spinal  and  sympathetic  systems.  In  the  loose 
tissue  external  to  the  tunica  albuginea  large  medullated  fibres 
are  observed ;  these  give  off  smaller  branches  which  enter  the 
cavernous  structure,  and  may  be  followed  for  some  distance  as 
medullated  or  non -medullated  fibres.  In  this  same  tissue  are 
found,  at  the  root,  shaft,  and  vicinity  of  the  corona  glandis, 
Pacinian  corpuscles.  They  are  oval  in  shape,  and  have  their 
long  diameter  parallel  to  the  long  axis  of  the  penis.  These 
bodies  have  also  been  met  with  in  the  cavernous  structure. 
The  glans  is  especially  rich  in  nervous  elements,  and  here  are 
found  bodies  known  as  the  "genital  nerve-corpuscles"  situated 
in  the  tissue  of  the  mucous  membrane  at  the  base  of  the  papil- 
lae. These  bodies  are  round  in  shape,  vary  in  size  from  0.1439 
to  0.2001  mm.  in  diameter,  and  have  characteristic  constrictions 
upon  their  surface,  giving  them  a  mulberry-like  appearance. 
The  ordinary  terminal  bulbs  of  Krause  are  also  met  with  in 
this  location. 

The  urethra  of  the  male  serves  as  the  excretory  canal  for 
the  urine  and  seminal  fluid.  An  anatomical  division  is  made 
into  the  prostatic,  membranous,  and  spongy  parts.  The  canal 
is  lined  with  a  mucous  membrane,  external  to  which  there  is  a 
fibrous  layer  rich  in  elastic  fibres,  having  a  cavernous  struc- 
ture ;  external  again  to  this  is  the  muscular  coat,  composed  of 
involuntary  muscular  fibres  arranged  in  two  layers,  an  internal, 
or  longitudinal,  and  an  external,  or  circular.  There  are  also 
numerous  fasciculi  of  oblique  fibres,  which  serve  to  connect  the 
two  layers. 

The  histological  structure  and  arrangement  of  the  three 
parts  of  the  urethra  are  unlike,  and  must  be  separately 
studied,  (a)  In  the  prostatic  portion  the  mucous  membrane 
lies  in  longitudinal  folds.  A  laminated  epithelium  covers  the 
inferior  wall,  while  the  sides  and  superior  wall  are  lined  with 
a  transitional  variety.  The  prominence  of  this  portion  of  the 
urethra,  the  colliculus  seminalis,  is  composed  of  elastic  tissue 
and  smooth  muscular  cells,  which  form  a  cavernous  structure. 
Throughout  this  spongy  tissue,  near  the  surface,  are  seen 
glands  similar  to  those  found  in  the  prostate.  Racemose  glands 
(Littre's  glands),  imperfectly  developed,  lined  with  cylindrical 

15 


226 


MANUAL    OF   HISTOLOGY. 


epithelial  cells  in  their  acini,  and  at  their  orifices  with  lami- 
nated epithelium,  are  also  present.  The  muscular  tissue  in 
this  part  of  the  urethra  is  intimately  connected  with  that  of 
the  prostate  ;  its  fasciculi  have  generally  a  longitudinal  direc- 
tion, and  send  off  oblique  bundles  into  the  mucous  mem- 
brane, (b)  The  membranous  por- 
tion of  the  urethra  has  its  mucous 
membrane  covered  by  an  epithe- 
lium similar  to  that  met  with  in 
the  prostatic  portion.  The  glands 
of  Littre  are  absent.  Beneath  the 
mucous  membrane  a  long-meshed 
erectile  tissue  of  a  cavernous  na- 
ture is  found.  Here  the  organic 
muscular  layer  is  poorly  devel- 
oped, and  it  is  covered  by  trans- 
verse bundles  of  striped  muscular 
fibres,  the  musculus  uretliralis.  (c) 
Passing  to  the  spongy  portion,  the 
mucous  membrane  is  found  thrown 
into  longitudinal  folds,  which  are 
in  places  connected  by  transverse 
ones,  forming  depressions,  known 
as  the  lacuncB  Morgagnii.  These 
are  not  glandular  in  their  nature. 
The  epithelium  covering  the  mu- 
cous membrane  in  this  portion  is 
mostly  cylindrical,  but  as  it  ap- 
proaches the  meatus  urinarius 
gradually  assumes  a  pavement 
character.  Glands  of  Littre  are  found  throughout  this  part. 
The  muscular  elements  are  even  less  prominent  here  than  in 
the  membranous  portion. 

Well-developed  and  numerous  papillae  are  seen  projecting 
from  the  mucous  membrane  of  the  urethra  into  the  epithelium. 
They  possess  a  single  capillary  loop,  or  several  loops  are  ob- 
served, especially  in  the  fossa  navicularis.  These  papillae  are 
absent  or  imperfectly  developed  at  the  points  where  a  transitional 
epithelium  is  met  with.  Here  the  capillaries  are  arranged  to  con- 
stitute a  reticulum  beneath  and  parallel  to  the  epithelial  covering. 
The  nerves  of  the  urethra  are  found  forming  a  network 


FIG.  103.— Transverse  section  through 
the  spongy  portion  of  the  urethra  (corpus 
cavernosum  nrethrae) :  &,  tunica  mucosa  ;  c, 
muscular  cords;  d,  vascular  spaces  of  the 
corp.  cavern.  ;  #,  glands ;  /,  excretory  duct 
of  gland  ;  g,  longitudinal  muscles ;  A,  tunica 
albuginea.  Klein. 


THE  MALE  ORGANS  OF  GENERATION.         227 

around  the  muscular  coat,  similarly  as  elsewhere,  in  connection 
with  smooth  muscular  fibres.  Small  nerve-fibres  have  been 
traced  into  the  epithelial  lining.  Collections  of  ganglionic 
nerve-cells  are  found  on  the  posterior  surface  of  the  membra- 
nous portion ;  in  the  dense  connective  tissue  at  the  posterior 
portion  of  the  bulb  ;  and  lastly,  in  the  network  of  nerve-fibres 
around  the  vessels  at  the  side  of  the  bulb. 

The  lymphatic  system  of  the  urethra  is  found  in  the  mu- 
cous membrane,  near  the  epithelium.  It  consists  of  a  network 
of  vessels  with  longitudinally  arranged  meshes  ;  they  are  con- 
nected with  the  lymphatic  vessels  of  the  bladder,  and  also  open 
into  the  lymphatic  canals  of  the  glans  penis. 

Cowper's  glands. — These  organs,  two  in  number,  are  situ- 
ated in  the  striated  muscular  tissue  which  surrounds  the  mem- 
branous portion  of  the  urethra.  They  are  lobulated,  oval,  and 
belong  to  the  jac^ttuaas^oup  of  glands.  They  are  composed 
of  acini  and  excretory  ducts  which  unite  to  form  a  single  duct 
for  each  gland,  and  discharge  into  the  bulbous  portion  of  the 
urethra.  [The  acini  constituting  the  several  lobules  are  separated 
by  connective  tissue  intermixed  with  smooth  muscular  fibres; 
they  possess  a  structureless  membrana  propria,  and  are  lined 
with  columnar  cells,  whiclTare  imbricated  upon  their  outer  thin 
portions.  The  ducts  are  lined  with  flattened  columnar  cells, 
and  a  layer  of  smooth  muscular  fibres  is  seen  running  along 
them.  A  capillary  network  surrounds  the  glandular  structure. 

The  prostate  may  be  described  as  a  glandular  organ,  pecu- 
liar in  having  its  stroma  composed  of  involuntary  muscular 
elements.  Externally  it  possesses  a  connective-tissue  envelope 
which  is  united  to  bands  of  smooth  muscular  fibres  that  run 
in  every  direction,  and  constitute  the  cortical  substance  of 
the  organ.  From  this  cortex  numerous  bands  or  trabeculze 
of  a  similar  muscular  nature  proceed,  forming  an  intricate 
network,  and  making  up  the  greater  part  of  the  gland  ;  in  the 
meshes  of  this  reticulum  is  placed  the  glandular  structure. 
The  thickness  of  the  cortex,  or  the  amount  of  glandular  sub- 
stance, varies  according  to  the  position,  whether  behind  or  in 
front  of  the  urethra,  and  it  is  found  that  the  glandular  struc- 
ture is  comparatively  more  developed  behind  and  in  the  lower 
portions  than  in  front  of  the  urethra. 


228 


MANUAL    OF    HISTOLOGY. 


The  arrangement  of  the  glandular  elements  is  similar  to 
that  in  the  racemose  glands,  and  consists  of  excretory  ducts  ter- 
minating in  glandular  vesicles  or  acini.  The  ducts  which  have 
their  orifices  in  the  urethra  at  its  prostatic  portion,  and  upon 
its  inferior  wall,  are  here  lined  with  a  transitional,  or,  when 
large,  with  a  pavement  epithelium,  which  gradually  changes 


f 


Pia.  104.— Transverse  section  through  the  caput  gallinaginia :  a,  epithelium  of  surface;  b,  vesicula 
prostatica  ;  c,  epithelium  of  the  vesicula  ;  <j,  muscles  ;  e,  ejaculatory  duct ;  /,  excretory  duct  of  the  pros- 
tatic glands ;  0,  upper  wall  of  the  urethra ;  muscles  running  vertically.  From  a  child.  Klein. 

into  a  columnar  variety  as  the  ducts  penetrate  the  organ.  The 
basement-membrane  is  structureless,  and  is  invested  by  a  mus- 
cular layer.  |  The  acini  are  also  lined  by  a  columnar  epithelium 
and  possess  a  structureless  membrana  propria ;  their  shape  is 
usually  pyriform,  and  they  have  a  diameter  varying  between 
0.1254  and  0.23  mm.  The  epithelial  cells  of  the  acini  frequently 
contain  granules  of  brownish  pigment. 


THE  MALE  ORGANS  OF  GENERATION. 


229 


cortex 
Paci- 


Transversely  striated  muscular  fibres  are  also  met  with  in 
the  prostate,  both  anterior  and  posterior  to  the  urethra,  ex- 
tending into  the  cortical  substance,  and  between  the  glandular 
structure  in  the  interior  of  the  gland. 

The  blood-vessels  of  the  organ  come  from  the  large  trunks 
surrounding  it ;  they  pass  into  its  structure  and  form  a  reticu- 
lated capillary  system  around  the  glandular  substance. 

Medullated  nerve-fibres  are  found  surrounding  the 
in  connection  with  groups  of  oval  gariglionic  centres, 
nian    bodies    are   also   ob- 
served in  the  cortex  of  the 
prostate,  and  in  its  interior 
are  small  medullated  nerve- 
fibres  which  form  a  reticu- 
lum. 

A  peculiar  structure  is 
found  in  the  upper  and  pos- 
terior part  of  the  prostate. 
It  has  the  appearance  of  a 
duct,  with  walls  resembling 
an  artery,  in  so  far  as  it 
consists  of  an  internal  longi- 
tudinal, a  middle  circular, 
and  an  external  longitudi- 
nal coat.  The  middle  coat  is  composed  mostly  of  smooth  mus- 
cular elements,  while  the  external  and  internal  coats  are  only 
partly  made  up  of  them.  The  interior  of  this  structure  is  filled 
with  a  rich  vascular  network,  pigment  particles,  and  smooth 
muscular  fibres. 

The  vesicula  prostatica,  which  forms  a  cul-de-sac  in  the 
middle  of  the  prostate,  beneath  the  middle  lobe,  opening  by  a 
duct  at  the  summit  of  the  colliculus  seminalis,  possesses  a 
fibrous  wall  in  which  there  are  smooth  muscular  cells  and  is 
surrounded  by  a  thin  layer  of  cavernous  tissue  ;  it  is  lined  by 
a  laminated  epithelium,  into  which  small  conical  papillae  pro- 
ject/, small  branched  and  tortuous  glands  are  also  found  open- 
ing into  its  cavity. 

The  testicles  are  glandular  organs  which  secrete  the  sper- 
matic fluid,  and  are  in  the  male  organism  the  sexual  represen- 
tatives of  the  ovaries  in  the  female. 


FIG.  105. — Transverse  section  through  the  central 
glandular  substance  of  the  prostate.  From  an  adult. 
Klein. 


230  MANUAL    OF    HISTOLOGY. 

The  glandular  structure,  together  with  the  epididymis  of  the 
testicles,  is  enveloped  by  a  dense  fibrous  membrane,  the  tunica 
albuginea.  This  is  surrounded  by  a  serous  sac,  the  tunica 
vaginalis  propria.  Finally  the  testicle  and  spermatic  cord  are 
invested  by  the  tunica  vaginalis  communis  and  the  whole  is 
contained  in  the  scrotum. 

The  tunica  albuginea  upon  its  external  surface,  or  that 
covered  by  the  tunica  vaginalis  propria,  is  smooth  and  shin- 
ing ;  it  consists  of  dense  connective  tissue  with  some  elastic 
fibres  ;  upon  the  posterior  border  of  the  testicle  it  increases  in 
thickness,  and  is  here  termed  the  corpus  Higlimori,  or  medias- 
tinum testis,  which  passes  into  the  gland.  It  also  sends  off 
from  its  whole  internal  surface  numerous  bands  or  trabeculse, 
the  septula  testis,  which  run  toward  the  mediastinum,  and 
divide  the  .interior  of  the  testicle  into  conical  lobules,  having 
their  apices  directed  toward  the  corpus  Higlimori.  These  tra- 
beculse  contain  smooth  muscular  fibres  and  blood-vessels.  It 
is  in  these  lobules  or  spaces  that  the  secreting  elements  of  the 
gland  are  situated. 

The  serous  sac,  or  tunica  vaginalis,  has  its  visceral  la}^er,  the 
tunica  adnata,  intimately  united  to  the  tunica  albuginea  over 
the  testicle,  but  it  is  loosely  attached  to  that  over  the  epididy- 
mis. This  membrane  consists  of  connective  tissue  traversed 
by  delicate  elastic  fibres,  and  lined  on  its  surface  with  a  layer 
of  polyhedral  cells,  varying  in  size  and  containing  oval  nuclei 
with  one  or  two  nucleoli.  Upon  the  upper  portion  of  the  tes- 
ticle and  sharp  edge  of  the  epididymis,  the  tunica  adnata  is 
frequently  found  to  possess  tufted  excrescences ;  these  pro- 
cesses are  covered  by  several  layers  of  flattened  epithelial  cells, 
or  a  single  layer  of  round  or  cylindrical -bodies.  A  capillary 
loop  is  seen  extending  into  the  tufts. 

The  parietal  layer  of  the  tunica  vaginalis  propria  consists 
of  connective  tissue,  elastic  fibres,  and  epithelium,  as  in  the 
visceral  layer. 

The  tunica  vaginalis  communis,  which  covers  the  tunica 
vaginalis  propria,  is  composed  above  of  a  loose,  laminated  con- 
nective tissue,  but  it  becomes  more  dense  below.  Between 
this  tunica  and  the  tunica  propria  unstriped  muscular  fibres 
are  found,  while  upon  its  external  surface  there  are  the  striped 
fibres  of  the  cremaster  muscle.  Small  non-vascular  peduncu- 
lated  excrescences  are  also  found  upon  this  surface.  The  mem- 


THE  MALE  ORGANS  OF  GENERATION".          231 

brane  is  connected  externally  by  connective  tissue  with  the 
muscular  layer  of  the  scrotum,  the  dartos. 

The  muscle  of  the  scrotum,  the  dartos,  consists  of  numerous 
smooth  muscular  fibres,  arranged  singly  or  forming  a  more  or 
less  continuous  layer. 

The  skin  of  the  scrotum  is  peculiar  in  containing  consider- 
able pigment,  while  there  is  an  absence  of  fat  in  the  subcu- 
taneous tissue.  Hairs,  large  sebaceous  follicles,  and  sweat- 
glands  are  also  present  in  the  skin  of  the  scrotum. 

The  Tiydatid  of  Morgagni  is  a  structure  found  upon  the 
anterior  surface  of  the  head  of  the  epididymis,  and  is  thought 
to  be  the  remains  of  Muller's  duct.  It  is  met  with  in  two 
forms,  either  as  a  vesicle  containing  a  clear  fluid  (with  cells, 
and  nuclei — ciliated  epithelial  cells  are  also  at  times  present), 
and  connected  to  the  epididymis  by  a  solid  fibrous  peduncle,  or 
as  a  flattened  structure  possessing  scarcely  any  stalk,  which 
is  simple  or  divided  into  lobules ;  the  latter  form  is  most  fre- 
quently seen.  At  times  it  is  found  to  communicate  with  the 
canal  of  the  epididymis. 

Between  the  head  of  the  epididymis  and  the  vas  deferens, 
situated  upon  the  posterior  edge  of  the  testicle,  a  small  organ 
is  seen,  consisting  of  several  whitish  nodules.  Each  nodule  is 
composed  of  a  tube  forming  a  number  of  convolutions  and  ter- 
minating in  a  club-shaped  extremity.  The  tubes  contain  a 
clear  fluid  and  are  lined  by  a  cylindrical  epithelium,  the  cells 
of  which  are  undergoing  degeneration.  Until  ten  years  of  age 
this  organ  is  fully  developed ;  after  this  period  it  experiences 
degeneration.  This  structure  is  known  as  the  organ  of  Gir- 
aldes,  and  represents  the  remains  of  the  Wolffian  bodies. 

The  glandular  or  parenchymatous  structure  of  the  testicle 
consists  of  canals  or  seminiferous  tubules  about  0.1128  to 
0.1421  mm.  in  diameter ;  they  are  folded  on  themselves  sev- 
eral times  so  as  to  constitute  lobules,  and  are  situated  in  the 
spaces  formed  by  the  trabeculse  of  the  tunica  albuginea.  The 
tubules  not  only  are  folded  but  divide  and  subdivide,  anasto- 
mose, and  terminate  by  loops.  Toward  the  apices  of  the  lob- 
ules the  tubules  gradually  become  more  straight,  fewer  in 
number,  and  pass  into  the  corpus  Highmori,  forming  the 
rete  testis.  From  the  upper  part  of  the  rete  emerge  twelve  to 
seventeen  larger  tubules  which  pass  through  the  tunica  albu- 
ginea, after  which  they  again  become  convoluted  and  form  a 


232  MANUAL    OF   HISTOLOGY. 

number  of  conical  lobules,  named  the  coni  vasculosi,  which 
form  the  head  of  the  epididymis.  These  tubules  gradually 
unite  to  form  a  single  canal,  which  is  much  convoluted,  and 
develops  an  elongated  body,  the  body  and  tail  of  the  epididy- 
mis. The  convolutions  becoming  less  and  less  marked,  the 
tube,  increased  in  calibre,  then  leaves  the  testicle  and  ascends, 
at  first  somewhat  spirally,  but  soon  after  in  a  perfectly  straight 
course,  constituting  the  vas  defer  ens.  Before  this  duct  is 
formed,  a  short  csecal  branch,  named  the  vas  dberrans,  is  at- 
tached to  the  tube. 

The  seminiferous  tubules  either  take  their  origin  from  blind 
extremities  or  anastomoses,  the  former  being  more  frequently 
met  with  in  children.  Surrounding  the  tubules  there  is  seen 
a  framework  of  connective  tissue,  which  proceeds  from  the 
septa.  This  intertubular  connective  tissue  is  distinctly  lam- 
inated, and  each  lamella  is  formed  of  a  fenestrated  endothe- 
lial  membrane,  and  a  fenestrated  connective- tissue  membrane, 
which  thus  constitute  numerous  communicating  spaces,  that 
are  the  rootlets  of  the  lymphatic  system  of  the  testis.  The 
number  of  lamellae  between  the  seminal  tubes  varies,  and  their 
relation  to  the  tubes  is  very  intimate,  but  depends  upon  the 
amount  of  fluid  present  in  the  interlamellar  lymph-spaces. 
Groups  of  peculiar  cells  are  found  between  the  lamellae  of  the 
intertubular  connective  tissue.  These  cells  have  been  observed 
by  histologists,  and  by  most  are  thought  to  be  connective-tissue 
corpuscles.  Klein,  however,  says  they  are  epithelial  in  nature, 
and  derived  from  the  epithelial  columns  of  the  Wolffian  body. 

In  the  meshes  formed  by  this  reticulated  fibrous  tissue  are 
located  the  seminiferous  tubules,  the  membrana  propria  of 
which  is  thought,  on  the  one  hand,  to  be  structureless,  or,  on 
the  other,  to  be  composed  of  oval,  flattened  corpuscles,  placed 
at  regular  intervals,  which  form  an  endothelial  membrane.  The 
tubules  are  found  filled  with  corpuscles.  Those  at  the  periphery 
covering  the  membrana  propria  are  round  or  polygonal  in  form, 
upon  transverse  section.  In  children,  the  cells  of  the  tubules 
contain  a  finely  granular  and  pale  substance,  but  in  adults 
they  are  filled  with  yellow  pigment.  Two  typical  forms  of  cor- 
puscle are  observed,  one  with  dark  granular  nuclei,  the  other 
with  bright  ones  that  have  or  have  not  nucleoli.  The  number 
of  nuclei  varies  ;  usually  there  are  one  or  two  ;  but  they  may 
reach  thirty  or  more.  Many  variously  formed  cells  are  seen, 


THE  MALE  ORGANS  OF  GENERATION.          233 

which  fact  is  held  to  indicate  active  proliferation.  These  bodies 
are  termed  seminal  cells,  and  in  the  embryo  are  said  to  possess 
contractility  and  amoeboid  movement. 

The  seminiferous  tubules  upon  entering  the  corpus  High- 
mori  lose  their  special  external  coat,  which  blends  with  the 
connective  tissue  of  this  region.  Their  epithelial  lining  con- 
sists of  cylindrical  cells  with  short  cilia.  After  leaving  tho 
corpus  Highmori  and  increasing  in  size,  they  have  an  additional 
coat  of  smooth  muscular  fibres,  which,  further  down  in  the 
body  of  the  epididymis,  consists  of  two  layers,  an  internal  and 
an  external  or  longitudinal  coat.  The  epithelium  lining  the 
canal  of  the  epididymis  is  composed  of  cells  with  long,  oval 
nuclei,  and  provided  with  long  tufts  of  cilia.  Indeed,  the  lar- 
gest cilia  found  in  the  human  body  are  upon  the  large  cylindri- 
cal cells,  which  cover  the  upper  part  of  the  canal  of  the  epi- 
didymis. Beneath  this  layer  of  ciliated  bodies  is  a  second  of 
small,  polyhedral  ones  with  round  nuclei. 

The  vas  deferens,  which  may  be  considered  as  analogous 
in  many  respects  to  the  excretory  duct  of  a  glandular  organ, 
is  made  up  of  an  external  or  fibrous  coat,  a  middle  or  mus- 
cular, and  a  mucous  membrane,  which  is  located  most  inter- 
nally. Covering  this  membrane  are  epithelial  elements  which 
differ  in  the  various  parts  of  the  duct.  At  the  beginning  there 
is  a  single  layer  of  cylindrical  cells,  between  which,  sometimes, 
there  are  spindle-shaped  bodies ;  the  former  possess  delicate 
cilia.  At  about  four  centimetres  from  the  epididymis  the  cilia 
are  lost,  but  the  character  of  the  cells  remains  the  same,  ex- 
cept that  a  striated  border  can  be  seen  in  many.  In  children, 
a  difference  exists  between  the  extra-  and  intra-abdominal  por- 
tions of  the  duct.  The  former,  or  extra,  is  lined  by  a  lami- 
nated epithelium,  composed  of  a  superficial  layer  of  short 
cylindrical  cells,  beneath  which  are  one  or  two  layers  of  round 
or  polyhedral  cells.  All  these  corpuscles  have  a  relatively 
large  nucleus.  The  intra-abdominal  portion  of  the  duct  has  a 
lining  similar  to  that  observed  in  the  adult. 

The  mucous  coat  is  made  up  of  connective  tissue  and  elas- 
tic fibres,  the  former  consisting  of  intersecting  fasciculi,  the 
latter  of  a  close  network.  The  membrane  is  thrown  into 
two  or  three  longitudinal  folds  or  rugae.  Near  the  lower  end 
of  the  vas  deferens,  in  the  ampulla,  the  longitudinal  folds 


234  MANUAL    OF    HISTOLOGY. 

are  connected  by  transverse  ones,  and  thus  depressions  are 
formed. 

The  muscular  coat  consists  of  smooth  muscular  fibres  ar- 
ranged in  three  layers  :  an  inner,  or  longitudinal,  which  is 
feebly  developed  ;  a  middle,  or  circular,  which  is  substantial  in 
character,  and  an  external  or  longitudinal.  This  coat  is  less 
developed  in  young  children  than  in  adults. 

In  the  external  fibrous  coat,  or  tunica  adventitia  of  the  vas 
deferens,  are  found  bundles  of  smooth  muscular  fibres  running 
longitudinally.  They  are  derived  from  the  cremaster  interims, 
which  muscle  is  well  developed  at  the  origin  of  the  vas  deferens, 
but  gradually  diminishes  in  size  as  it  enters  the  abdominal  cavity. 

The  vas  deferens  possesses  a  dense  plexus  of  medullated 
nerve-fibres,  the  spermatic  plexus,  situated  in  the  tunica  ad- 
ventitia. From  this  plexus  several  smaller  trunks  proceed 
which  penetrate  into  the  muscular  and  mucous  coats.  Scat- 
tered along  these  nerve- trunks  are  seen  small  ganglion- cells, 
which  are  round  or  oval. 

The  blood-vessels  of  the  testicle  come  from  the  internal 
spermatic  artery  and  enter  the  gland  partly  at  the  corpus 
Highmori  and  partly  upon  its  surface.  They  surround  the 
seminiferous  tubules  as  a  capillary  plexus  of  large  meshes. 
The  epididymis  receives  its  blood  from  the  deferential  artery, 
and  also  to  some  extent  from  the  vessels  of  the  testicle.  The 
was  deferens  possesses  a  rich  capillary  network  in  its  muscular 
coat  and  also  in  its  mucous  membrane  beneath  the  epithelium. 

The  nerves  of  the  testicle  come  from  the  internal  spermatic 
plexus ;  their  mode  of  termination  has  not  as  yet  been  satis- 
factorily explained.  \  Letzerich,  however,  describes  fine  nerve- 
fibres  in  the  testicles  of  mammals ;  they  penetrate  the  connec- 
tive tissue  and  membrana  propria,  terminating  between  this 
layer  and  the  first  row  of  cells  in  dark  granular  masses. 

The  lymphatic  system  of  the  testicle  consists  of  a  series  of 
lacunae,  lined  with  endothelial  cells,  which  surround  the  semi- 
niferous tubules ;  in  the  interstitial  connective-tissue,  these 
communicate  with  canals  from  which  others  are  given  off  to 
the  connective-tissue  septa  of  the  lobules.  Beneath  the  tunica 
albuginea  another  network  of  lymphatic  canals  is  also  found, 
which  penetrate  the  tunic,  especially  upon  the  dorsum  of  tbe 
organ,  and  finally,  uniting  with  the  lymphatics  of  the  epididy- 


THE  MALE  ORGANS  OF  GENERATION.          235 

mis  and  tunica  vaginalis,  form  several  large  trunks,  which  fol- 
low the  spermatic  cord.  Distinct  networks  of  lymphatic  ves- 
sels are  found  in  the  vascular  and  nervous  layers  of  the  sper- 
matic cord,  and  some  are  seen  close  to  the  muscular  coat  of  the 
vas  deferens. 

The  seminal  vesicles,  designed  as  receptacles  for  the  fluid 
secreted  by  the  testicles,  are,  with  some  slight  modifications, 
similar  in  structure  to  the  vas  deferens.  They  are  composed 
of  a  mucous,  muscular,  and  fibrous  coat.  The  mucous  mem- 
brane is  covered  with  a  superficial  layer  of  cylindrical  and  a 
deep  layer  of  polyhedral-epithelial  cells,  and  is  thrown  into 
folds,  longitudinal  and  transverse,  forming  depressions.  The 
muscular  coat  consists  of  three  layers,  an  internal  or  longi- 
tudinal, a  middle  or  circular,  and  an  external  or  longitudinal. 
The  fibrous  coat  is  abundantly  supplied  with  networks  of  ves- 
sels and  nerves.  Here  the  ganglionic  collections  are  highly 
developed,  each  corpuscle  being  quite  large  and  containing  a 
single  nucleus,  or  even  at  times  two. 

The  ejaculatory  ducts  are,  histologically,  similar  to  the  last 
described  organs.  As  they  approach  the  prostate  their  cylin- 
drical epithelium  gradually  changes  into  the  transitional  va- 
riety, and  subsequently  into  the  laminated  pavement,  as  they 
approach  their  point  of  outlet  in  the  urethra.  Their  mucous 
membrane  is  uneven  from  the  longitudinal  and  transverse 
folds.  After  entering  the  prostate  the  muscular  substance  of 
the  ducts  undergoes  cavernous  transformation. 

When  the  testicle  attains  its  full  physiological  develop- 
ment, which  occurs  in  man  at  puberty,  there  is  secreted  by  the 
organ  a  peculiar  fluid,  the  semen  or  sperma.  This  fluid  is 
whitish,  slimy,  and  colorless,  and  has  an  alkaline  or  neutral  re- 
action. Semen  examined  as  discharged  from  the  orifice  of  the 
urethra,  in  coitu,  appears  as  a  very  different  fluid,  having  re- 
ceived the  secretions  from  the  various  accessory  glands  of  the 
generative  system.  It  is  now  more  fluid,  opaque,  strongly  al- 
kaline in  reaction,  and  has  acquired  a  peculiar  odor.  Placed 
under  the  microscope  there  is  seen  suspended  in  a  hyaline  fluid 
an  infinite  number  of  moving  thread-like  bodies  called  seminal 
filaments,  spermatozoa,  spermatozoids,  seminal  elements,  etc. 
They  are  divided  into  a  head,  body  or  middle  portion,  and  tail. 


236 


MANUAL    OF    HISTOLOGY. 


FIG.  106. — Seminal  elements  of 
man:  «,  undeveloped;  &,  mature. 
St.  George. 


They  are  as  follows 


The  shape  of  the  head  is  pyriform,  the  broad  part  being  con- 
nected with  the  body  ;  each  has  an  average  length  of  0.0045 
mm.,  and  its  breadth  is  about  half  as  much.  The  middle  por- 
tion or  body  is  about  0.0061  mm.  long,  while  the  tail  measures 

about  0.0406  mm.  Both  the  body  and 
head  of  the  seminal  elements  seem  to 
be  rigid,  the  terminal  thread  or  tail 
having  an  active  motion.  From  this 
description  it  will  be  seen  that  a  com- 
parison of  its  structure  with  that  of  a 
ciliated  epithelial  cell  is  admissible,  and 
indeed  quite  reasonable. 

The  way  in  which  spermatozoa  are 
formed  is  still  imperfectly  known,  and 
two  different  views  claim  our  attention. 
a.  The  nucleus  of  the  seminal  cells 
moves  to  the  periphery,  then  at  the  opposite  side  the  proto- 
plasm of  the  cell  is  elongated  into  a  caudal  appendage ;  the 
nucleus  continuing  to  advance  causes  the  protoplasm  to  be- 
come more  and  more  elongated,  and  it  is  ultimately  lengthened 
into  a  thread-like  tail,  while  the  nucleus,  with  its  thin  layer  of 
protoplasm,  constitutes  the  head.  b.  In  this  view  the  columnar 
or  prismatic-shaped  cells,  the  most  external  layer  of  cells  fill- 
ing the  seminal  tubules,  are  thought  to  be  the  spermatozoa- 
producing  elements.  The  inner  .remaining  cells  of  the  tu- 
bules experience  no  further  development.  During  the  active 
stage  of  the  gland  the  spermatic  cells  become  elongated,  and 
extend  into  the  centre  of  the  tubule  ;  their  free  extremities 
become  enlarged,  and  have  a  number  of  buds  or  club -like  pro- 
jections, eight  to  twelve,  developed  upon  them.  In  each  bud 
is  formed  a  nucleus ;  these  nuclei  eventually  become  the 
heads  of  spermatozoa,  and  the  protoplasm  is  further  developed 
into  the  body  and  tail.  The  cells  from  which  the  spermatozoa 
have  their  origin  are  named  spermatoblasts. 

Klein,  in  his  recent  "Atlas  of  Histology,"  gives  a  very  ex- 
tended description  of  the  development  of  spermatozoa.  Ac- 
cording to  this  writer  there  are  several  layers  of  epithelial 
cells  lining  the  inside  of  the  membrana  propria  of  the  seminal 
tubules.  These  layers  he  divides  into  an  outer  and  inner. 
The  outer,  situated  next  to  the  membrana  propria,  embraces 
the  germ-cells  of  Sertoli.  The  inner  layer,  those  nearer  the 


THE  MALE  ORGANS  OF  GENERATION.          237 

lumen  of  the  tubule,  are  the  seminal  cells  of  Sertoli.  These 
latter  are  usually  arranged  in  two  or  more  layers,  polyhedral 
in  shape  when  placed  closely  together,  but  more  spherical  when 
next  to  the  lurnen  of  the  tubule  ;  they  are  uniform  in  size  and 
contain  a  single  nucleus.  The  nucleus  is  spherical,  possesses 
no  limiting  membrane,  and  contains  a  convolution  of  thick 
fibrils,  or  rods,  in  a  transparent  matrix.  A  more  minute  ex- 
amination of  the  nucleus  shows  that  the  fibrils  are  arranged  in 
certain  definite  forms,  which  indicate  changes  preparatory  to 
division,  as  has  been  pointed  out  by  Strassburger,  Hertwig, 
Flemming,  and  others.  The  various  forms,  taken  by  the  nucleus 
before  dividing,  correspond  to  what  is  termed  the  "convolu- 
tion," the  "basket,"  the  "wreath,"  the  "monaster,"  or  the 
"  dy aster."  The  entire  process  of  the  indirect  division  of  the 
nucleus  is  termed  by  Flemming  TcaryoTcinesis. 

Toward  the  lumen  of  the  tube  the  above- described  cells  are 
seen  with  their  nucleus  either  dividing  or  divided  into  two 
daughter -nuclei.  From  these  daughter-nuclei  are  developed 
the  daughter-cells,  or  spermatoblasts,  and  by  an  interesting 
series  of  changes  the  spermatozoa  are  formed. 

"The  nucleus  of  the  spermatoblasts  at  first  retains  its  spher- 
ical shape,  but  is  invested  in  a  distinct  membrane,  the  convo- 
lution of  fibrils  changes  into  a  honey-combed  reticulum,  some- 
times with  one  or  two  nucleoli,  and  the  nucleus  is  not  placed 
in  the  centre  but  in  the  periphery  of  the  cell." 

"  Next  the  nucleus  becomes  uniform  in  its  substance  and 
transparent,  all  traces  of  a  reticulum  have  disappeared.  The 
cell-substance  has  collected  at  one  end  of  the  nucleus  as  an 
elliptical  granular  mass,  and  appears  separated  from  it  by  a 
transparent,  clear  bag." 

"  In  the  next  stage  the  nucleus  becomes  flattened  and  dis- 
coid, so  that  when  viewed  from  the  surface  it  is  broad  and  cir- 
cular, but  appears  narrow  and  staff-shaped  when  seen  in  profile. 
The  cell-substance  at  this  time  is  drawn  out  into  a  cylindrical 
or  club-shaped  granular  body,  separated  from  the  nucleus  by 
a  shorter  or  longer  clear  tube,  the  former  clear  bag.  At  the 
front  part  of  the  nucleus  is  seen  a  short  and  tapering  curved 
projection,  and  at  its  hind  end — viz.,  that  directed  toward  the 
clear  tube  and  cell-substance — there  is  also  to  be  found  a  short- 
pointed  process  extending  into  the  clear  tube  just  named." 

"  In  the  next  stage  the  nucleus  becomes  more  flattened  and 


238  MANUAL    OF    HISTOLOGY. 


oblong.  In  the  last  stage  the  granular  body  has  become 
changed  into  a  long,  thin,  and  homogeneous  filament." 

"  In  what  relation  do,  then,  these  different  parts  of  the  fully 
formed  spermatozoon  stand  to  the  parts  of  the  developing  ele- 
ment— that  is,  the  spermatoblast?  A  comparison  shows  at 
once  that  the  head  of  the  ripe  spermatozoon  is  the  changed 
nucleus  of  the  spermatoblast ;  that  the  filament,  or  tail,  is  de- 
rived from  what  has  been  mentioned  above  as  the  granular 
body  of  the  original  cell.  The  middle  piece  of  Schweigger- 
Seidel  is  an  outgrowth  of  the  nucleus  of  the  spermatoblast, 
that  is,  of  the  head,  the  spermatozoon,  and  the  clear  tube  of 
the  developing  spermatozoon,  described  above  as  embracing 
the  hind  part  of  the  nucleus  and  separating  the  latter  from 
the  granular  body,  is  the  sheath  which,  in  some  instances 
(triton  and  salamander),  is  observable  on  the  middle  piece  of 
the  fully  formed  spermatozoon." 

In  short,  the  head  of  the  spermatozoon  is  derived  from  the 
nucleus,  while  the  tail  has  its  origin  from  the  body  of  the  sper- 
matoblast. 


BIBLIOGRAPHY. 

^COOPER,  A.     Obs.  on  the  Struct,  and  Dis.  of  the  Testis.     London,  1830. 
•  WAGNER.     Muller's  Archiv.     1836. 

•PANIZZA,  B.     Osservazioni  anthropo-zoot.  -fisiol.     Pavia,  1836. 
•VALENTIN.     Ueb.  d.  Verl.  d.  Blutgef.  im  Penis  d.  Menschen.    Mailer's  Arch.    1838. 
?KOBELT.     Die  mannl.  u.  weibl.  Wollustorgane.     Freiburg-,  1844. 
KOLLIKER.     Gewebelehre  und  Verhandl.  d.  Wiirzb.  med.-phys.  Ges.     1851. 
^KOHLRAUSCII.     Zur  Anat.  u.  Phys.  d.  Beckenorgane.     Leipzig,  1854. 
TAPPET.     L'urethre  de  rhomme.     1854. 
LEYDIG,  F.    Zur  Anat.  d.  mannl.  Geschlechtsorg.  in  Zeitschr.  f.  wiss.  Zool.    Vol.  II. 

And  Histologie.     1857. 

» JARJAVAY.     Rech.  anat.  sur  I'urethre  de  rhomme.     Paris,  1857. 
•MERKEL.     Gottinger  Nachrichten.     No.  1.  p.  7.     1863.     And  Arch.  f.   nrikr.  Anat. 

Vol.  I.,  p.  309.     1865. 
r  ST.  GEORGE,  v.  LA  VALETTE  in  Arch.  f.  mikr.  Anat.     Vol.  I.,  p.  403.    1865.    And 

Strieker's  Manual. 

'PETTIGREW,  in  Proc.  Roy.  Soc.     Vol.  XV.,  p.  244.     1866. 
*  SCHWEIGGER-SEIDEL,  in  Virch.  Arch.     Vol.  XXXV1L,  p.  225.    1866. 
»  BALBIANA.     Journal  de  1'anat.  et  de  la  phys.,  p.  218.     1868. 
«  LETZERICH.  in  Virch.  Arch.     Vol.  XLII.,  p.  570.     1868.  - 

«  STIEDA.     Ueber  den  Bau  des  Menschen-Hoden,  Arch.  f.  mikros.  Anat.     Vol.  XIV., 
p.  17.     1877. 


BIBLIOGEAPHY.  239 

-SERTOLI.     Sulla  struttura  di  canalicoli  seminif.  del  testicoli.     Arch.  p.  le  scien. 

med.     Vol.  II.,  p.  107.     1877. 

•  MENZEL.     Ueber  Spermatozoon.    Arch.  f.  klin.  Chir.     Vol.  XXI.,  p.  518.     1877. 
<VALENTIN,  in  Zeitschr..  f.  rat.  Med.     Vol.  XVIII.,  p.  21.     Vol.  XXI.,  p.  39.     1879. 
CLANGER,  in  Wien.  Sitz.     Vol.  XL VI.,  p.  120.     1879. 
*  ROUGET.     Compt.  rend.     Vol.  IV.,  p.  902.     1879. 
*FREY,  HEINRICH.     Histology  and  Histochemistry  of  Man.     1880. 
KLEIN,  E.,  and  SMITH,  E.  NOBLE.    Atlas  of  Histology.     J880. 


CHAPTEK  XVI. 

THE  FEMALE  EXTEENAL  AND  INTEENAL  OEGANS  OF  GENERA 
TION,  WITH  THEIE  GLANDULAR  APPENDAGES— PLACENTA. 

BY  DR.  J.  HENRY  C.  SIMES, 
Lecturer  on  Histology,  University  of  Pennsylvania. 

THE  external  female  genitals  are  the  labia  majora,  labia 
minora,  and  clitoris. 

The  labia  majora  are  folds  of  skin,  the  subcutaneous  tis- 
sue of  which  contains  a  large  amount  of  adipose  tissue.  Their 
internal  surface  has  the  nature  of  a  mucous  membrane,  while 
externally  it  is  similar  to  the  common  integument.  Here  hairs, 
sebaceous  glands,  remarkable  for  their  large  size,  and  sweat- 
glands,  are  found.  The  papillae,  vessels,  nerves,  and  Pacinian 
corpuscles  do  not  differ  from  those  found  elsewhere  in  the  skin. 

The  labia  minora  may  be  considered  as  folds  of  mucous 
membrane.  They  are  covered  by  a  laminated  pavement-epi- 
thelium and  the  deepest  layer  contains  pigment  granules. 
Conical  vascular  papillae  are  seen  beneath  the  epithelium. 
In  the  connective- tissue  framework  of  the  mucous  membrane 
smooth  muscular  elements  are  found.  Capillary  networks  are 
seen  on  the  surface  beneath  the  epithelium,  and  in  the  sub- 
stance of  the  membrane,  from  which  arise  small  veins,  consti- 
tuting a  plexus,  and  giving  this  structure  the  character  of  an 
erectile  tissue.  Upon  the  external  surface  of  the  folds  are  found 
sebaceous  glands  without  hairs.  These  glands  are  absent  at 
birth.  There  is  no  adipose  tissue  in  the  labia  minora. 

The  clitoris  is  covered  by  a  mucous  membrane  which  is  a 
continuation  of  that  of  the  labia  minora,  and  to  which  it  is 
similar  in  structure,  in  so  far  as  epithelium,  mucous  tissue,  and 
papillae  are  concerned.  The  mucous  membrane  covering  the 
glans  of  the  organ  is  found  to  have  those  peculiar -terve-termi- 
nations  in  its  structure,  the  genital  nerve-corpuscles,  which 


THE  FEMALE  ORGANS  OF  GENERATION.        241 

have  been  described  as  existing  in  the  mucous  membrane  of 
the  glans  penis. 

Beneath  the  mucous  membrane  of  the  clitoris  are  found  the 
corpora  cavernosa  and  glans  /  the  latter  is  in  connection  with 
both  bulbi  vestibuli,  which  correspond  to  the  corpus  spongio- 
sum  urethrse  of  the  male.  These  structures  consist  of  erectile 
or  cavernous  tissue,  which,  like  that  in  the  penis,  is  made  up  of 
a  vascular  network,  mostly  venous  in  character,  and  erectile  in 
nature  ;  they  are  also  surrounded  by  a  fibrous  tunic  analogous 
to  the  tunica  albuginea  of  the  penis. 

The  vestibule  has  its  mucous  membrane,  which  is  a  con- 
tinuation of  the  mucous  membrane  of  the  clitoris,  thrown  into 
a  number  of  folds.  Opening  upon  its  surface  .are  numerous  ori- 
fices of  racemose  mucous  glands.  These  glands  are  collected 
into  groups  around  the  orifice  of  the  urethra  and  vagina.  They 
consist  of  branched  ducts,  which  at  their  deeper  parts  are  de- 
veloped into  a  number  of  acini ;  they  are  lined  with  a  simple 
epithelium  ;  at  their  orifices  they  have  the  laminated  pavement- 
epithelium  of  the  mucous  surface.  These  glands  vary  in  diame- 
ter between  0.5  mm.  to  2.5  mm.  The  vessels  of  the  vestibule 
form  a  network  near  the  mucous  surface,  and  are  connected  to 
the  capillary  loops  in  the  papillae. 

Opening  upon  each  side  of  the  vaginal  entrance  is  the  orifice 
of  the  duct  belonging  to  the  gland  of  BartTioline.  These  or- 
gans, two  in  number,  are  analogous  to  Cowpers  glands  in  the 
male.  They  belong  to  the  racemose  group,  and  are  composed 
of  ducts  and  acini,  which  have  an  epithelium  lining  of  cylin- 
drical cells. 

The  hymen  consists  of  a  duplicature  of  the  mucous  mem- 
brane of  the  vagina.  Its  laminated  epithelium  is  similar  to 
that  of  the  vestibule.  The  papillae  are  numerous,  long,  simple 
or  multiple,  and  project  from  0.2  to  0.3  mm.  into  the  epithelial 
covering.  The  vascular  and  nervous  supply  is  very  abundant. 

The  vagina  consists  of  an  external  coat  of  connective  tissue, 
a  middle  coat  of  muscular  tissue,  and  an  internal  mucous  coat. 
The  mucous  membrane  is  uneven,  thrown  into  ridges  and  papil- 
lary elevations,  which  are  especially  well-marked  in  the  neigh- 
borhood of  the  vaginal  entrance.  The  epithelium  lining  the 
canal  is  a  laminated  pavement-epithelium,  into  which  the  vas- 

16 


242  MANUAL    OF    HISTOLOGY. 

cnlar  papillae  of  the  mucous  membrane  extend.  In  the  latter 
coating  are  found  numerous  elastic  fibres  in  the  fasciculi  of 
connective  tissue ;  bundles  of  smooth  muscular  cells  are  also 
present.  Tubular  glands,  lined  with  ciliated  columnar  epithe- 
lium at  their  fundus,  have  been  described  as  existing  in  the 
mucous  membrane  of  the  vagina  by  Preuschen.  Hennig  also 
speaks  of  similar  glands  being  present  in  this  membrane.  The 
submucous  tissue  is  very  vascular  and  loose  in  texture.  The 
muscular  coat  consists  of  an  internal  longitudinal  and  an  ex- 
ternal circular  layer  of  smooth  muscular  fibres,  between  which 
are  many  oblique  connecting  fasciculi.  The  external  fibrous 
tissue  is  loose  in  texture,  and  has  embedded  in  it  the  external 
venous  plexus. 

The  vascular  system  of  the  vagina  is  composed  of  arteries, 
veins,  a  venous  plexus,  and  capillaries.  The  plexus  is  met 
with  in  the  folds  of  the  vagina.  It  is  a  cavernous  structure 
possessing  smooth  muscular  fibres,  and  has  an  arrangement  of 
rtrabeculae  similar  to  that  found  in  other  erectile  organs. 

The  lymphatics  and  nerves  of  the  mucous  membrane  of  the 
Tagina  are  abundant.  The  latter  form  networks  in  which  there 
are  found  ganglion-cells,  in  groups  or  single ;  as  in  the  male 
genitals,  these  cells  are  of  two  sizes.  The  ultimate  terminations 
of  the  nerve-fibres  are  as  yet  undetermined.  The  fluid  secreted 
iby  this  membrane  has  an  acid  reaction. 

The  urethra  possesses  a  mucous  membrane  covered  by  a 
-transitional  epithelium  at  its  upper  portion,  the  superficial 
layer  of  cells  being  short  cylinders,  which  gradually  become 
shorter,  until  the  deepest  layer  is  seen  made  up  of  rounded  cells. 
'The  lower  portion  of  the  canal  has  a  lining  of  laminated  pave- 
ment-epithelium similar  to  that  of  the  vestibule.  The  mucous 
membrane  has  numerous  papillae  extending  into  the  epi- 
thelium. In  this  layer  are  seen  at  places  many  lymph-corpus- 
cles, sometimes  amounting  to  an  infiltration,  when  it  may  be 
considered  as  adenoid  in  nature.  The  submucous  tissue  is 
mostly  composed  of  venous  networks  ;  it  is  in  fact  a  cavernous 
tissue.  As  in  the  male,  there  are  present  in  the  mucous  mem- 
brane the  glands  of  Littre,  seen  especially  abundant  near  the 
meatus  urinarius.  The  muscular  coat  of  the  urethra  consists 
of  an  internal  longitudinal  and  an  external  circular  layer  of 
smooth  muscular  fibres  ;  in  the  external  layer  are  also  the 


THE  FEMALE  ORGANS  OF  GENERATION.        243 

transversely  striated  muscular  fibres  of  the  urethral  muscles. 
The  external  fibrous  coat  of  the  urethra  consists  of  wavy  con- 
nective-tissue fasciculi,  which  have  a  longitudinal  and  circular 
course. 

The  uterus  possesses  an  external  covering  of  serous  mem- 
brane, the  peritoneum  ;  anteriorly  it  is  more  intimately  con- 
nected with  the  organ  than  posteriorly,  while  at  the  sides  the 
layers  are  separated,  in  order  to  permit  the  passage  of  blood- 
vessels, lymphatics,  and  nerves  into  the  uterine  substance. 
The  tissue  composing  the  greater  part  of  the  uterus  is  formed 
of  smooth  muscular  fibres,  the  arrangement  of  which  is  very 
irregular,  but  three  more  or  less  distinct  layers  have  been  de- 
scribed. The  external  one,  which  is  relatively  thin,  consists 
mostly  of  fibres  running  longitudinally,  although  many  circu- 
lar fasciculi  are  seen.  The  middle  layer  exceeds  the  others  in 
thickness,  its  fibres  take  a  longitudinal,  transverse,  or  oblique 
direction,  while  the  internal  layer  is  essentially  circular,  and 
forms  the  sphincters  of  the  uterus.  The  contractile  elements 
of  these  muscular  layers  are  intimately  united  together  by  a 
cementing  substance,  forming  fasciculi  or  bundles,  which  are 
again  held  together  by  connective  tissue  in  which  elastic  fibres 
are  found.  The  shape  of  the  cells  in  the  normal  uterus  is  fusi- 
form, frequently  very  long,  and  in  transverse  section  round  or 
oval,  with  several  angles.  The  nucleus  is  always  single,  rod- 
like  or  oblong  in  shape. 

The  mucous  membrane  lining  the  uterus  is  closely  connected 
to  the  muscular  tissue.  It  has  no  connective-tissue  framework 
of  fibres,  but  its  structure  resembles  the  stroma  of  lymphoid 
organs,  in  which  the  framework  is  made  up  of  spindle  and 
fusiform  cells.  The  surface  of  this  membrane  varies  in  differ- 
ent parts ;  at  the  fundus  and  body  it  is  smooth,  except  at  the 
orifices  of  the  Fallopian  tubes,  where  there  is  a  slight  folding ; 
in  the  canal  of  the  neck  it  is  thrown  into  numerous  branching 
folds,  the  plicce  palmatce.  At  the  upper  end  of  the  isthmus  of 
the  cervix  a  distinct  border  indicates  the  termination  of  the 
mucous  membrane  of  the  body.  The  epithelium  covering  this 
portion  of  the  membrane  is  columnar  in  shape,  and  provided 
with  short  cilia.  There  are  found  in  the  mucous  membrane 
of  the  fundus  and  body  numerous  tubular  glands,  which  are 
either  simple  tubes  or  they  divide  about  their  middle,  and  ter- 


244  MANUAL   OF   HISTOLOGY. 

minate  in  blind  ends;  frequently  they  have  a  spiral  course, 
corkscrew-like  ;  bat  generally  their  direction  is  vertical  to  the 
plane  of  the  membrane ;  they  open  into  the  cavity  of  the 
uterus.  The  existence  of  a  membrana  propria  in  these  glan- 
dulce  utriculares  is  denied  by  some,  or  if  present  it  is  only 
toward  the  orifice  of  the  gland.  In  the  pregnant  organ,  how- 
ever, an  extremely  delicate,  structureless  membrane,  in  which 
oval  nuclei  are  found,  is  thought  to  represent  such  a  structure. 
The  cells  lining  these  glands  are  prismatic  in  shape,  their  broad 
ends  directed  outward  ;  the  slender  extremities  projecting  into 
the  lumen  of  the  gland  are  provided  with  cilia. 

The  mucous  membrane  lining  the  canal  of  the  cervix  is 
denser  and  thicker  than  that  of  the  body.  It  possesses  a  con- 
nective-tissue investment  which  lies  between  it  and  the  muscu- 
lar layer,  and  it  also  differs  from  the  lining  of  the  body  in  the 
presence  of  folds,  which  constitute  the  plicae  palmatse.  The 
epithelium  covering  this  portion  of  the  uterus  is  made  up  of 
cylindrical  ciliated 'cells,  in  the  upper  two-thirds  of  the  canal, 
but  as  the  external  os  uteri  is  approached  it  gradually  as- 
sumes the  laminated  pavement  variety.  Minute  papillae,  pro- 
vided with  a  capillary  loop,  are  found  in  the  lower  half  of  the 
canal.  The  folds  of  membrane  consist  of  a  firm  fibrous  tissue, 
a  few  smooth  muscular  elements,  and  a  scanty  amount  of  elas- 
tic fibres.  Here  are  also  located  the  mucous  follicles  of  the 
cervix,  or,  as  some  histologists  consider  them,  depressions  only 
of  the  mucous  membrane ;  they  are  lined  with  a  cubical  epi- 
thelium, and  possess  a  structureless  membrana  propria,  which 
is  intimately  connected  to  the  connective  tissue.  From  an 
occlusion  of  the  orifices  of  these  follicles  there  are  developed 
small  retention  cysts  containing  mucoid  fluid,  usually  round  or 
oval,  and  measuring  0.3  to  0.5  mm.  in  length  ;  they  are  known 
as  the  ovula  Ncibotlii.  The  fluid  secreted  by  the  mucous  mem- 
brane of  the  uterus  differs  from  that  of  the  vaginal  mucous 
membrane  in  having  an  alkaline  reaction. 

The  mucous  membrane  covering  the  intra-vaginal  portion 
of  the  uterus  is  a  continuation  of  the  vaginal  mucous  mem- 
brane, consisting  of  a  similar  structure,  and  composed  of  a 
connective-tissue  framework  with  papillae  projecting  into  its 
covering  of  laminated  pavement-epithelium.  At  times  this  por- 
tion is  found  to  contain  the  ovula  Nabothi. 

The  uterus  is  a  very  vascular  organ  ;  a  capillary  network  is 


THE  FEMALE  ORGANS  OF  GENERATION".        245 

found  in  the  muscular  coat  and  mucous  membrane.  In  the 
latter  such  reticula  are  seen  to  surround  the  glands.  The  veins 
are  very  large,  possess  delicate  walls,  and  are  valveless.  In  the 
cervical  portion,  a  more  regular  distribution  of  vessels  is  met 
with,  and  their  walls  are  unusually  thick. 

Numerous  lymphatic  vessels  are  found  beneath  the  peri- 
toneal covering  of  the  uterus,  and  arched  passages  are  seen 
ending  in  loops  or  blind  extremities  under  the  mucous  mem- 
brane of  the  cervix.  Lymph  clefts  and  vessels  are  also  met 
with  in  the  intermuscular  connective- tissue. 

The  nerves  of  the  uterus  are  derived  from  the  genital  sper- 
matic ganglia.  On  the  posterior  wall  of  the  neck  a  large 
ganglionic  mass  is  met  with,  from  which  most  of  the  nerves 
have  their  origin.  Nervous  filaments  may  be  followed  as  far 
as  the  mucous  membrane,  and  a  few  histologists  have  traced 
them  into  the  papillae  of  the  cervix,  while  in  the  muscular  coat 
they  are  said  to  terminate  in  the  nuqlei  of  the  muscular  ele- 
ments. 

During  the  physiological  function  of  menstruation  and 
gestation  the  uterus  experiences  certain  modifications.  In  the 
former  there  is  an  increase  in  the  size  of  the  organ,  owing  mostly 
to  the  great  increase  of  blood  in  the  vessels  ;  the  glands  of  the 
mucous  membrane  are  also  increased  in  size.  The  discharge  of 
blood  during  this  period  is  due  either  to  a  rupture  of  the  dis- 
tended capillaries,  or  a  diapedesis,  in  which  the  walls  remain 
uninjured.  On  microscopical  examination  of  the  menstrual 
fluid  it  is  found  to  contain,  besides  the  blood-elements,  numer- 
ous uterine  epithelial  cells. 

The  modifications  of  the  uterus  during  gestation  occur  es- 
pecially in  the  muscular  elements,  which  are  greatly  hyper- 
trophied,  and  there  is  also  a  new  formation  of  them.  The 
blood-vessels,  lymphatics,  and  nerves  also  experience  an  in- 
crease in  size,  the  latter  by  a  thickening  of  their  perineurium. 
The  mucous  membrane  of  the  body  of  the  uterus  during  gesta- 
tion is  separated  from  the  uterus,  previously  becoming  thicker, 
softer,  and  more  vascular,  and  constitutes  the  decidua.  The 
cervical  portion  of  the  mucous  membrane  does  not  participate 
in  this  metamorphosis  ;  it  retains  its  epithelium,  and  secretes  a 
mucous  plug,  which  fills  the  canal  of  the  cervix  during  preg- 
nancy. Subsequent  to  delivery  a  new  mucous  membrane  and 
glands  are  developed  on  the  cavity  of  the  uterus,  and  the  hy- 


240  MANUAL    OF   HISTOLOGY. 

pertropliied  and  newly  formed  muscular   elements  undergo 
retrograde  development  and  fatty  metamorphosis. 

The  Fallopian  tubes,  or  temporary  ducts  of  the  ovary,  con- 
sist of  an  external  covering  furnished  by  the  peritoneum,  rich 
in  connective  tissue  and  blood-vessels  ;  a  muscular  coat  made 
up  of  an  outside  layer  of  longitudinal,  and  an  inside  layer  of 
circular  involuntary  muscular  elements  ;  and,  finally,  an  in- 
ternal mucous  membrane.  A  division  of  the  tube  is  made  into 
two  parts:  that  toward  the  uterus,  into  which  it  opens,  the 
much  narrower  portion,  is  the  isthmus,  while  the  free  half  is 
the  ampulla,  which  terminates  in  the  fimbrice.  The  mucous 
membrane,  upon  transverse  section  of  the  tube,  in  the  narrow 
portion,  is  seen  thrown  into  simple  longitudinal  folds,  while  in 
the  ampulla  the  folds  are  much  more  complicated,  and  in  a 
transverse  section  have  a  dendritic  appearance.  The  epithelium 
covering  the  mucous  membrane  consists  of  ciliated  columnar 
epithelial  cells.  The  movements  of  the  cilia  occasion  a  current 
in  the  direction  of  the  uterine  opening.  There  is  an  absence  of 
glands  in  the  mucous  membrane  of  the  Fallopian  tubes.  The 
same  histological  elements  are  present  in  the  fimbrise  as  in 
other  portions  of  the  tube,  of  which  they  are  a  direct  contin- 
uation. 

The  ovary  for  histological  study  may  be  divided  into  two 
parts,  the  cortex  and  medullary  substance ;  covering  the  cor- 
tex is  a  layer  of  columnar  epithelial  cells,  named  the  ovarian 
or  germ  epithelium  (Fig.  107).  In  a  perpendicular  section,  the 
germ-epithelium  is  here  and  there  seen  to  extend  down  into 
the  substance  of  the  organ  and  form  tubes — the  ovarial  tubes. 
The  cortical  substance  or  parenchymal  zone  consists  of  several 
layers  of  dense  connective  tissue,  in  which  are  found  ovarial 
tubes  and  ovarian  follicles.  The  most  external  follicles  are  im- 
perfectly developed,  while  those  lying  deeper  are  more  highly 
developed  and  contain  the  ovum.  Internal  to  the  cortex  is  the 
medullary  substance  or  vascular  zone,  in  which  are  numerous 
blood-vessels,  giving  it  the  nature  of  a  cavernous  tissue. 

The  stroma  of  the  ovary  consists  of  fibrillar  connective  tis- 
sue. In  the  vascular  zone  it  is  somewhat  loose  in  texture,  and 
contains  a  network  of  elastic  tissue.  There  are  also  found  in 
this  zone  fasciculi  of  smooth  muscular  fibres,  which  follow  the 


THE  FEMALE  ORGANS  OF  GENERATION. 


247 


large  and  medium  sized  arteries,  afc  times  constituting  a  sheath 
for  the  vessels.  In  the  stroma  of  the  parenchymal  zone  the 
connective- tissue  forms  an  outer  layer  of  short,  dense  fibres 


FIG.  107. — From  the  ovarium  of  a  rather  old  bitch ;  portion  of  a  sagittal  section,  a,  germ-epithelium ; 
ft,  &,  ovarial  tubes ;  c,  c,  younger  follicles ;  d,  older  follicle  ;  e,  discus  prollgerus,  with  egg ;  /,  epithelium 
of  a  second  egg  in  the  same  follicle ;  flf,  tunica  fibrosa  folliculi  ;  A,  tunica  propria  folliculi ;  i,  follicular 
epithelium  (membrana  granulosa);  £,  collapsed,  degenerated  follicle;  f,  vessels:  TO,  TO,  cell-tubes  of  the 
parovarium,  both  longitudinal  and  transverse  sections ;  j/.  tubular  sinking  in  of  the  germ-epithelium  into 
the  substance  of  the  ovary ;  «,  commencement  of  the  germ- epithelium  close  to  the  lower  border  of  the 
ovary.  Waldeyer. 


which  run  in  every  direction,  and  an  inner  one  abounding  in 
cells,  in  which  the  follicles  are  seen. 

The  blood-vessels  enter  the  ovary  at  the  hilum.  The  arteries 
have  a  spiral,  corkscrew-like  course  through  the  organ.  At 
the  hilum  the  veins  form  a  convoluted  mass,  the  bulb  of  the 


248  MANUAL    OF    HISTOLOGY. 

ovary.     A  capillary  reticulum  surrounds  tlie  follicles,  and  is 
situated  in  their  internal  membrane. 

The  stroma  of  the  hilum  contains  numerous  lymphatics, 
which  have  an  arrangement  similar  to  that  of  the  veins.  Sur- 
rounding the  follicles  in  their  external  lamina  is  found  a  dense 
network  of  lymphatics. 

The  nerves  enter  the  ovary  at  the  hilum  with  the  arteries, 
and  they  have  been  followed  into  the  stroma  between  the  large 
follicles,  but  their  ultimate  terminations  have  not  as  yet  been 
ascertained. 

The  follicles  of  the  ovary,  or  Graqfian  follicles,  consist  of  a 
connective-tissue  wall  separable  into  two  layers :  an  internal, 
which  contains  the  small  capillaries,  and  an  external,  contain- 
ing the  large  blood-vessels  and  lymphatics.  The  outer  layer  is 
made  up  of  the  same  connective  tissue  as  the  stroma  of  the 
ovary,  in  which  are  numerous  spindle-shaped  cells.  The  inter- 
nal layer  consists  of  connective  tissue,  in  which  are  numerous 
and  variously  shaped  cells,  fusiform,  stellate,  and  small  round 
bodies,  the  latter  possessing  amoeboid  movement ;  there  are 
also  seen  larger  round  or  polygonal-shaped  cells.  This  layer  of 
corpuscles  is  the  membrana  granulosa.  Within  the  follicle, 
and  distending  it,  is  an  albuminous  fluid  holding  a  few  bodies 
in  suspension.  Situated  in  the  follicle,  usually  at  that  part 
most  distant  from  the  surface  of  the  ovary— although  this  is 
not  a  rule  without  exception,  since  it  is  also  found  immediately 
below  the  most  superficial  part  of  the  follicle — the  ovum  is 
found  surrounded  by  a  collection  of  cells  of  the  granular  mem- 
brane, known  as  the  discus  proligerus.  Two  kinds  of  cells 
form  the  discus  proligerus,  the  follicular  and  egg  epithelium  ; 
the  latter  lie  in  immediate  contact  with  the  vitelline  membrane, 
and  are  closely  adherent  to  it. 

An  examination  of  the  mature  ovum  demonstrates  it  to 
measure  0.28  to  0.1379  mm.  in  diameter ;  it  is  spherical  in 
shape,  and  is  a  typical  cell,  consisting  of  an  investing  mem- 
brane, the  vitelline  membrane,  or  zona  pellucida,  which  is 
a  dense,  transparent,  homogeneous  substance,  apparently 
pierced  by  numerous  minute  pores.  This  membrane  is  prob- 
ably developed  from  the  cells  of  the  discus  proligerus,  and  from 
the  layer  described  as  the  egg  epithelium.  The  cell-contents, 
protoplasm,  or  vitellus  is  a  granular  mass  composed  of  albu- 
minous and  fatty  particles,  and  a  more  or  less  distinct  reticu- 


THE  FEMALE  ORGANS  OF  GENERATION. 


249 


lum  of  fine  fibrils.  Within  the  vitellus  is  seen  the  nucleus  or 
germinal  vesicle  (also  presenting  a  delicate  reticulum  of  fibrils), 
situated  eccentrically,  spherical  in  shape,  measures  0.037  to 
0.451  mm.  in  diameter,  shining,  transparent,  and  contains  the 
nucleolus  or  germinal  spot,  which  is  a  highly  refractile  body, 
finely  granular,  supposed  to  be  non-vesicular,  and  measures 
0.0046  to  0.0068  mm.  in  diameter. 

The  mature  Gfraafian  follicle,  which  is  seen  on  the  surface 


FIG.  108.— 4,  primordial  egg  of  the  human  being ;  8  months1  fcetus.  B,  primordial  follicle  of  the 
rabbit.  <7,  primordial  follicle  of  a  dove.  D,  a  somewhat  older  follicle  of  the  same  animal ;  commence- 
ment of  the  formation  of  the  subordinate  yolk.  E,  blind  end  of  the  ovary  of  an  ascaris  nigrovenosa ; 
germinal  vesicles  (some  of  which  possess  a  germinal  spot  and  Schron's  ''granule")  in  a  diffuse  mass  of 
protoplasm.  F,  egg  of  the  ascaris  nigrovenosa  from  about  the  middle  of  the  ovary ;  Schron's  granule ; 
commencement  of  the  deposition  of  yolk-matter.  <?,  egg  from  a  follicle  (2  mm.  in  diam.)  of  the  rabbit  : 
a.  egg-epithelium;  &,  striated  zone  with  radiating  striae ;  c,  germinal  vesicle;  d,  germinal  spot ;  e,  yolk. 

of  the  ovary,  giving  rise  to  a  prominence,  ruptures  during  the 
menstrual  period  and  empties  its  contents,  viz.  :  the  ovum, 
fluid  contents,  and  discus  proligerus  into  the  Fallopian  tube. 
The  cause  of  the  rupture  is  an  increase  in  the  contents  of  the 
follicle,  and  a  fatty  metamorphosis  of  the  cells  of  the  wall  of 
the  follicle.  As  a  result  of  this  rupture  of  the  Gfraafian  vesi- 
cle, there  is  formed  a  yellow  body,  the  corpus  luteum,  which 


250  MANUAL    OF   HISTOLOGY. 

reaches  its  full  development  in  a  few  weeks  after  the  raptur- 
ing of  the  follicle,  or  when  impregnation  has  occurred  after  the 
lapse  of  two  or  three  months.  It  consists  of  a  central  portion, 
at  first  red,  becoming  gray,  and  a  peripheral  portion,  yellow  in 
color,  thrown  into  folds.  These  folds  are  made  up  of  the  in- 
ternal membrane  and  cells.  The  central  portion  in  a  fresh 
corpus  luteum  consists  of  a  very  vascular  tissue,  in  which  are 
seen  numerous  large  cells,  containing  a  red  coloring  substance 
and  hsematoidin  crystals.  A  retrograde  metamorphosis  occurs 
in  the  yellow  body,  supposed  to  be  due  to  a  want  of  nutrition 
caused  by  a  wasting  of  the  arteries,  and  there  only  remains  a 
white  cicatrix,  the  corpus  albicans.  The  time  required  for 
the  disappearance  of  a  corpus  luteum  when  impregnation  has 
taken  place — a  true  corpus  luteum — is  several  months,  lasting 
to  the  end  of  gestation ;  but  for  the  disappearance  of  a  false 
corpus  luteum,  or  when  impregnation  has  not  occurred,  it  only 
requires  a  few  weeks.  It  is,  however,  to  be  remembered,  that 
every  Graafian  follicle  with  its  contents  does  not  reach  full  de- 
velopment ;  most  of  them  experience  fatty  or  colloid  metamor- 
phosis. 

The  ovaries  have  their  origin  from  the  Wolffian  bodies.  A 
thickening  of  the  epithelial  covering  is  early  observed  upon 
the  side  of  these  bodies ;  at  the  same  time  and  place  a  cellular 
projection  growing  from  the  connective  tissue  of  the  organ  is 
noticed.  From  this  increase  of  epithelium  the  Graafian  folli- 
cles and  ova  are  developed,  later  the  ovarial  epithelium  ;  from 
the  connective  tissue  is  built  up  the  vascular  system  of  the  ovary. 

The  Graafian  follicles  are  developed  from  collections  of  cells, 
irregular  in  shape,  or,  as  they  are  named,  ova  chains,  consisting 
of  small-sized  peripheral  cells,  which  later  form  the  membrana 
granulosa,  and  the  primordial  ova  ;  these  last  are  recognized 
by  their  large  size,  granular  or  reticulated  protoplasm  and 
central  position.  The  ova  chains  are  sometimes  enclosed  in  a 
homogeneous  membrana  propria,  forming  a  tubular  structure, 
as  in  the  cat ;  this  membrane,  however,  is  not  found  in  all  ani- 
mals. These  chains  are  developed  by  an  ingrowth  of  the  epi- 
thelial cells  covering  the  surface  of  the  ovary. 

The  parovarium,  or  remains  of  the  Wolffian  body,  situated 
in  the  broad  ligament,  is  made  up  of  twelve  to  fifteen  tubules, 
which  possess  a  membrana  propria,  lined  by  a  single  layer  of 
ciliated  epithelium,  and  contain  a  transparent  substance. 


THE  FEMALE  ORGANS  OF  GENERATION.        251 

The  placenta  is  divided  into  a  uterine  and  foetal  portion. 
The  former  consists  of  cells  irregular  in  shape,  containing  one 
or  several  nuclei,  and  at  times  one  or  more  nucleoli.  These 
cells  are  separated  by  an  intercellular  substance,  either  hyaline, 
granular,  or  fibrous  in  nature.  Fusiform  cells,  in  which  a  rod- 
shaped  nucleus  is  seen,  are  also  found,  and  are  thought  to  in- 
dicate the  presence  of  smooth  muscular  elements.  The  tufts 
upon  the  surface  of  the  uterine  placenta,  which  divide  and  sub- 
divide, pass  quite  deeply  into  the  foetal  placenta,  yet  no  direct 
transformation  of  them  into  the  foetal  tissue  can  be  demon- 
strated ;  they  appear  to  terminate  in  fibrillated  tissue,  which 
contains  none  of  the  cellular  elements  of  the  uterine  placenta. 

The  blood-vessels  of  the  uterine  placenta  are  arteries  and 
veins,  with  no  intermediary  capillary  system  ;  they  communi- 
cate by  means  of  sinuous  spaces,  limited  by  placental  tissue 
only.  These  spaces  are  said  to  possess  a  delicate  limiting  wall ; 
this  statement,  however,  has  not  been  confirmed. 

The  foetal  placenta  is  developed  from  the  chorion,  the  villi 
or  tufts  of  which  growing  into  the  uterine  follicles  are  covered 
by  a  columnar  epithelium.  The  blood-vessels  in  the  villi  do 
not  lie  directly  in  contact  with  the  wall  of  the  villus,  but  are 
separated  from  it  by  a  perivascular  space.  Besides  a  direct 
communication  of  the  arteries  and  veins,  there  is  also  a  capil- 
lary system  present  in  the  villi.  Connective  tissue  accompa- 
nies the  vessels  into  the  villi  from  the  chorion.  The  variety  of 
connective  tissue  here  met  with  is  the  mucoid,  consisting  of 
round,  spindle,  and  stellate-shaped  cells,  with  a  structureless 
intercellular  substance.  There  is  a  direct  transformation  of 
this  mucoid  connective  tissue  into  the  connective  tissue  of  the 
chorion. 


BIBLIOGRAPHY. 

BISCIIOFF.     Beitr.  zur  Lebre  v.  d.  menschl.  EihtLllen.     1834. 

VALENTIN,  in  Muller's  Arch.,  p.  526.     1838. 

GOODSIR.     Anat.  and  Path.  Researches.     Edinburgh,  1845. 

KOBELT.     Der  Nebeneierstock  des  Weibes.     Heidelberg,  1847. 

STEINHN.     Ueber  d.   Entw.    d.  Graaf.  Foil.  u.  Eier  d.  Saugeth.,  Mittheil.  d.  ZU- 

richer  naturf.  Gesellsch.     1847. 
ROBIN.     Arch,    gener.    de  med.     Vol.  XVII.,  p.   258  and  405.     1848.     And  Vol. 

XVIII.,  p.  257.     Also  Gaz.  med.     No.  50.     1855. 
BAINEY,  in  Phil.  Trans.,  II.     1850. 


252  MANUAL    OF   HISTOLOGY. 

SCHRODER  VAN  DER  KOLK.    Waarnemingen  oves  liet  Maaksel  van  de  menschl. 

Placenta,  etc.     Amsterdam,  1851. 

SMITH,  TYLER-.     Med.  Chir.  Trans.     Vol.  XXXV.,  378.     1852. 
KEMAK.    Unters.  ueb.  d.  Entwick.  d.  Wirbelthiere.      Berlin,  1855.     Med.  Centr. 

Zeit.     No.  42.     1861.     No.  3.     1862. 
KLEBS,  in  Virch.  Arch.     Vol.  XXVIII.     1863. 

PPLUGER,  E.    Ueb.  d.  Eierstocke  d.  Saugeth.  u.  d.  Menschen.     Leipzig,  1863. 
SPIEGELBERG.    Virch.  Arch.     Vol.  XXX ,  p.  466.  1864. 
KAMENEW.     Unters.  d.   Blutgef.  d.  Mutterth.  d.  Placenta,  Medicinsky  Westnik. 

No.  13.     1864. 
CORNIL,  in  Jour,  de  1'anat.,  p.  386.     1864.     Unters.  aus  d.  phys.  Labor,  zu  Bonn, 

p.  173.     Berlin,  1865. 

POLLE.     Die  Nerveuverbr.  in  d.  weibl.  Genital.     Gottingen,  1865. 
His,  in  Arch.  f.  mikr.  Anat.     Vol.  I.,  p.  151.     1865. 

ST.  GEORGE,  v.  LA  VALETTE,  in  Arch.  f.  mikr.  Anat.     Vol.  II.,  p.  56.     1866. 
PERIER.    Anat.  et  phys.  de  Fovaire.     Paris,  1866. 
STRICKER.     Wien.  Sitz.     June,  1866. 

LANGHANS,  in  Virch.  Arch.     Vol.  XXXVIII.,  p.  543.     1867. 
FRANKENHAUSER.     Die  Nerven.  d.  Gebarmutter.     Jena,  1867. 
JASSINSKL     Zur  Lehre  ueb.  d.  Struct,  d.  Placenta.    Virch.  Arch.     1867. 
VIRCHOW.     Bildg.  d.  Placenta,  in  Gesamm.  Abhandlungen.   1853. 
BIDDER.     Ueb.  Hist.  d.  Nachgeb.,  in  Hoist's  Beitr.  z.  Gynacol.    II.     1867. 
ERCOLANI.     Giamb.  delle  gland,  otricolare,  etc.     Bologna,  1868. 
PLIKOL,  in  Arch.  f.  mikr.  Anat.     VoL  V.,  p.  445.     1869. 
FRIEDLANDER.     Unters.  ueb.  d.  Uterus.    1870. 
HENNIG.     Der  Catarrh  d.  inn.  weibl.  Geschlechtsorg.     1870. 
WALDEYER.     Eierstock.  u.  Ei.     Leipzig,  1870. 
LOTT  and  A.  ROLLET.     Untersuchungen.     II.    Leipzig,  1871. 
LANGHANS.    Unters.  ueber  d.  menschl.  Placenta.     Arch.  f.  Anat.  u.  Phys.     1877. 
LEOPOLD.     Stud.  ueb.  d.  Uterus-schleimhaut.     Arch.  f.  Gyn.    Vol.  XI.,  p.  110  and 

443.     1877.    Also  Vol.  XII.,  p.  169.     1877. 

HENNIG.     Ueber  Driisen  der  Vagina.    Arch.  f.  Gyn.    Vol.  XII.,  p.  488.     1877. 
FOULIS.     The  Development  of  the  Ova,  and  the  Structure  of  the  Ovary,  etc.     Jour. 

of  Anat.  and  Phys.     Vol.  XIII.,  p.  353.     1878-79. 
FREY,  HEINRICH.     Histology  and  Histochemistry  of  Man.    1880. 
KLEIN,  E.,  and  E.  NOBLE  SMITH.    Atlas  of  Histology.    1880. 


CHAPTER  XVII. 

THE  BESPIBATOBY  TBACT. 

BY  BENJAMIN  F.  WESTBROOK,  M.D., 

Lecturer  on  Anatomy  and  Pathological  Anatomy  at  the  Long  Island  College  Hospital, 

Brooklyn,  N.  Y. 

THE  respiratory  tract  includes  the  nares  and,  perhaps,  the 
pharynx,  but  as  the  latter  is  more  commonly  associated  with 
the  function  of  deglutition,  and  the  former  contain  in  their 
tipper  portions  the  organs  of  one  of  the  special  senses,  they 
have  been  assigned  to  other  portions  of  this  work.  This  chap- 
ter is  devoted  exclusively  to  the  consideration  of  those  parts 
which  are  concerned  in  the  respiratory  process.  As  the  pleura 
forms  a  part  of  the  lung,  and  facilitates  the  movements  of 
breathing,  its  structure  may  properly  be  described  under  this 
section. 

The  air-tubes  are  in  general  made  up  of  three  layers :  an 
outer  of  connective  tissue  and  elastic  fibres  ;  a  middle,  muscu- 
lar and  cartilaginous;  and  an  inner  of  mucous  membrane. 
Their  structure  is  more  complex  in  the  upper,  and  simpler  in 
the  lower  portions  of  the  respiratory  passages. 

The  larynx. — The  muscles  of  the  larynx  are  of  the  striped 
or  voluntary  variety. 

The  ligaments  and  membranes  are  composed  of  yellow  elas- 
tic fibres  with  some  white  fibrous  tissue.  Their  structure  can  be 
easily  demonstrated  by  the  process  of  teasing  or  by  employing 
the  reagents  ordinarily  used  for  this  class  of  tissues.  The  la- 
teral thyro-hyoid  and  the  inferior  thyro-arytenoid  ligaments 
have  the  following  peculiarities  of  structure :  the  lateral  thyro- 
hyoid  ligament  usually  encloses  a  small  piece  of  hyaline  carti- 
lage about  the  size  and  shape  of  a  large  grain  of  wheat.  It 
is  known  as  the  cartilago  triticea.  In  adult  males  it  is  usually 
calcified.  It  may  be  incorporated  either  with  the  cornu  of  the 
hyoid  bone  or  with  the  superior  cornu  of  the  thyroid  cartilage. 


254  MANUAL   OF   HISTOLOGY. 

The  inferior  thyro-arytenoid  ligaments,  or  true  weal  cords, 
are  made  up  almost  entirely  of  yellow  elastic  fibres  stretched 
across  from  the  thyroid  cartilage  in  front,  to  the  vocal  processes 
and  adjacent  anterior  borders  of  the  arytenoids  behind.  The 
elastic  bundles  originate,  anteriorly,  in  a  mass  of  connective 
tissue  which  occupies  the  angle  of  the  thyroid.  Posteriorly, 
many  of  the  fibres  are  prolonged  into  the  arytenoid  cartilage, 
converting  that  part  of  it  into  reticular  tissue.  These  liga- 
ments are  continuous  below  with  the  lateral  crico-thyroid  mem- 
branes, and  are  described  by  some  anatomists '  as  their  superior 
borders. 

The  innermost  fibres  of  the  internal  thyro-arytenoid  mus- 
cle mingle  with  the  outer  fibres  of  this  ligament,  some  ending 
in  or  taking  their  origin  from  them.  The  intimate  relation  be- 
tween the  muscle  and  the  ligament  can  be  seen  in  a  vertical  sec- 
tion through  the  larynx. 

Of  the  laryngeal  cartilages,  the  three  larger  are  of  the 
hyaline  variety.  Horizontal  sections  show  a  broad  central  area 
with  two  zones  between  it  and  either  the  outer  or  inner  sur- 
face. The  appearance  of  the  zones  or  bands  is  thus  described 
by  Rheiner  : a  "  1.  A  thin  peripheral  portion,  appearing  to  the 
naked  eye  as  a  narrow,  bluish,  opalescent  band,  which  con- 
sists of  a  transparent  and  longitudinally  striated  matrix  with 
elongated  cartilage- cells  arranged  parallel  to  the  surface.  2. 
The  intermediate  layer,  a  narrow,  whitish,  opaque  band,  con- 
sisting of  a  dull  yellowish  ground-substance  with  numerous 
large  mother-cells  containing  fatty  daughter-cells.  3.  The 
broad  central  layer,  with  a  perfectly  transparent  homogeneous 
matrix  and  few  cells.  The  intercellular  substance  increases, 
relatively  to  the  contained  cells,  from  without  inward,  and,  in 
the  interior,  presents  numerous  large  spaces  in  which  no  cells 
are  found.  In  the  thyroid  and  cricoid  cartilages  the  outer 
peripheral  zone  is  thicker  arid  more  easily  distinguished  than 
the  inner." 

The  following  peculiarities  are  to  be  noted :  the  central  por- 
tion of  the  thyroid,  viz.,  that  part  which  forms  the  anterior 
projection  or  angle,  is  distinguished  by  the  great  number  and 
small  size  of  its  cells.  It  is  penetrated  by  numerous  fibres 

1  Quain's  Anatomy,  eighth  edition,  Vol.  II. ,  p.  284. 

2  Quoted  by  Merkel  in  Anatomic  u.  Phys.  des  mensch.  Stimm-  u.  Sprach-Organs. 
Leipzig,  1863,  S.  166. 


THE   RESPIRATORY   TRACT.  255 

from  that  mass  of  connective  tissue  from  which  the  vocal  cords 
take  their  origin.  After  prolonged  maceration  in  some  alka- 
line solution,  this  cartilage  can  be  separated  into  three  parts — 
two  lateral  and  an  anterior  or  median. 

The  arytenoids  are  not  composed  exclusively  of  hyaline 
cartilage.  The  vocal  process,  as  already  mentioned,  presents  a 
yellow  reticulated  structure,  the  fibres  of  which  are  continuous 
with  those  of  the  true  vocal  cords.  The  apex  has  also  a  re- 
ticular  structure  when  there  is  no  joint  between  it  and  the 
cartilage  of  Santorini.  The  elastic  tissue  is  then  continuous 
with  that  which  connects  it  with  the  corniculum.  A  hori- 
zontal section  through  the  arytenoid  at  the  level  of  the  vocal 
process  shows  the  reticular  structure  of  the  process,  the  hya- 
line character  of  the  body  of  the  cartilage,  and  the  gradual 
transition  from  one  to  the  other. 

The  three  cartilages  already  described  are  subject  to  calci- 
fication and  partial  ossification.  This  occurs  more  frequently 
and  at  an  earlier  age  in  the  male  than  in  the  female.  It  also 
begins  at  a  later  date  in  those  who  have  been  castrated.  It 
makes  its  first  appearance  at  the  points  of  muscular  attach- 
ment. As  the  cartilages  undergo  calcification  they  increase  in 
size,  so  that  the  calcified  larynx  of  old  age  is  larger  than  that 
of  the  young  adult.  The  matrix  also  splits  up  into  a  fibrous 
texture,  not  affected  by  acetic  acid. 

The  cornicula  laryngis  or  cartilages  of  Santorini  and  the 
cuneiform  cartilages  of  Wrisberg,  as  well  as  the  sesamoid 
cartilages  (when  they  exist)  are  of  the  reticulated  variety. 
The  cartilago  triticea  is  hyaline  and  prone  to  calcification. 

The  epiglottis  consists  of  reticular  cartilage.  On  transverse 
section,  however,  the  intercellular  substance  is  seen  to  be  a 
spongy  elastic  substance,  granular  on  section  ;  at  the  periphery 
yellow  fibres  are  present.  The  elastic  cartilage  should  be  ex- 
amined with  a  high  power. 

The  mucous  membrane  of  the  larynx  varies  in  its  structure 
in  different  situations.  On  the  laryngeal  surface  of  the  epi- 
glottis it  is  thin. 

The  epithelium  in  the  upper  half  is  in  several  layers.  The 
deepest  cells  are  somewhat  columnar  or  pyramidal  in  form, 
while  the  superficial  ones  are  flat.  The  lower  half  is  covered  by 
a  stratified,  columnar,  ciliated  epithelium.  The  epithelium  rests 
upon  a  thin,  apparently  structureless  basement-membrane. 


256  MANUAL    OF   HISTOLOGY. 

The  nmcosa  is  made  up  of  delicate  connective-tissue  fibres,  en- 
closing in  their  meshes  a  series  of  lymph-spaces.  Connective- 
tissue  cells  are  also  found  here,  and  some  elastic  fibres.  There 
are  a  few  small  papillae  in  the  upper  portion.  The  submucous 
layer  is  thin,  contains  many  elastic  fibres,  and  is  continuous 
with  the  perichondrium.  It  contains  the  racemose  mucous 
glands,  whose  ducts  open  upon  the  surface.  Some  of  the  larger 
glands  are  lodged  in  the  depressions  of  the  cartilage,  and  some 
are  even  situated  on  its  anterior  aspects,  their  ducts  passing 
through  to  the  posterior  side. 

In  the  submucous  tissue  there  are  lymphatic  follicles,  some 
of  which  are  arranged  about  the  mucous  glands  and  their  ducts. 

The  membrane  covering  the  false  vocal  cords,  arytenoid 
cartilages,  and  ary-epiglottic  folds,  as  well  as  that  lining  the 
ventricles  and  inferior  compartment  of  the  larynx  is  thicker 
and  more  loosely  attached  to  the  subjacent  parts.  It  is  covered 
by  stratified  columnar,  ciliated  epithelium,  except  upon  the 
edge  of  the  false  vocal  cords  and  over  the  inner  surfaces  of  the 
arytenoids,  where  it  is  of  the  pavement  variety.  The  mucosa 
contains  a  large  amount  of  lymphoid  tissue,  which  holds  in  its 
meshes  lymphoid  cells.  Closed  lymph-follicles  are  also  found 
in  the  submucous  tissue  of  the  false  vocal  cords  and  on  the 
floor  of  the  ventricle.1  That  portion  of  the  mucous  membrane 
which  covers  the  true  vocal  cords  is  thin,  more  closely  attached, 
and  has  no  mucous  glands.  In  its  anterior  half  it  has  numer- 
ous small  papillae  (0.07  to  0.08  mm.  in  height,  Coyne)  project- 
ing at  the  edge  and  on  the  superior  and  inferior  surfaces  of  the 
cord.  They  are  composed  of  connective  tissue,  with  many  elas- 
tic fibres.  Their  vascular  supply  is  slight.  The  membrane  in 
this  situation  is  covered  by  stratified  pavement -epithelium, 
continuous  posteriorly  with  that  which  covers  the  inner  sur- 
faces of  the  arytenoids.  Numerous  racemose  glands  send  their 
ducts  obliquely  upward  and  inward  to  discharge  their  secretion 
upon  the  upper  and  under  surfaces  of  the  vocal  cords. 

In  front  of  the  corniculum  laryngis,  on  either  side,  is  a  col- 
lection of  racemose  glands  surrounding  the  cartilage  of  Wris- 
berg.  Another  collection  is  found  between  the  arytenoids. 

The  epithelium  can  be  examined,  either  by  scraping  it  from 
the  surface,  or  in  sections.  The  mucous  glands  are  best  seen 

1  Coyne  :  Archiv.  d.  Physiologie,  p.  92,  1874. 


THE    RESPIRATORY    TRACT.  257 

in  sections  of  the  hardened  larynx.  They  are  lined  by  cubical 
glandular  epithelium.  The  capillary  blood-vessels  of  the  laryn- 
geal  mucous  membrane  are  small  with  wide  meshes,  giving  the 
membrane  a  paler  appearance  than  that  of  the  pharynx. 

The  lymphatics  are  numerous  in  the  mucous  and  sub- 
mucous  layers.  They  may  be  injected  with  Berlin  blue,  by 
puncturing  the  submucous  tissue. 

In  the  nervous  filaments  are  ganglion  cells.  The  mode  of 
termination  is  not  definitely  known.  But  in  the  mucous 
membrane  of  the  epiglottis  end  bulbs  have  been  found.  The 
methods  of  examination  will  be  found  elsewhere. 

The  trachea  and  primary  bronclii. — The  rings  of  the  trachea 
and  bronchi  are  composed  of  hyaline  cartilage.  Longitudinal 
sections  of  these  rings  show  that  the  cells  lying  near  the  peri- 
phery, underneath  the  perichondrium,  are  flattened,  and  ar- 
ranged with  their  long  axes  parallel  to  the  surface.  Internally 
they  are  oblong  and  perpendicular  to  the  former. 

The  ends  of  the  incomplete  rings  are  connected,  posteriorly, 
by  a  layer  of  smooth  muscular  fibres,  which  are  attached  to 
the  fibrous  tissue  of  the  perichondrium.  The  attachment  is 
to  the  inner  aspect  of  the  ends  of  the  cartilages,  so  as  to  throw 
the  muscular  layer  forward  of  the  most  posterior  projection  of 
the  rings. 

These  muscular  fibres  also  exist  in  the  spaces  between  the 
rings,  where  they  are  attached,  on  either  side,  to  the  fibrous 
tissue  of  the  tube.  Outside  of  the  transverse  fibres  are  a  few 
filaments  which  have  a  longitudinal  direction.  They  are  at- 
tached to  the  fibrous  membrane. 

The  fibrous  membrane  which  encloses  the  cartilages  and 
completes  the  framework  of  the  tube  is  composed  of  connective 
tissue  containing  a  considerable  portion  of  elastic  tissue,  par- 
ticularly in  its  external  portion.  The  outer  layer  of  the  fibrous 
membrane  encloses  both  the  cartilages  and  the  muscle  fibres. 
The  inner  layer  is  thin  and  lies  between  the  rings  and  the 
glandular  layer. 

The  mucous  membrane  is  covered  by  several  layers  of  epi- 
thelial cells,  the  deeper  being  more  or  less  spherical  or  ovoid, 
whilst  the  superficial  ones  are  columnar  and  ciliated.  The 
columnar  cells,  losing  their  cilia,  are  continued  into  the  ducts 
of  the  mucous  glands.  These  glands  are  very  numerous,  and 
often  of  considerable  size.  They  are  racemose,  the  acini  being 


258 


MANUAL    OF    HISTOLOGY. 


lined  with  cubical  epithelium.  Owing  to  the  distention  of  some 
of  the  gland-cells  by  mucus  or  by  the  action  of  reagents,  they 
assume  a  rounded  form,  and  the  nuclei  are  pressed  against  the 
attached  ends  of  the  cells.  Such  corpuscles  are  known  as 
"  goblet "  cells.  Some  of  the  larger  glands  project  posteriorly 
outside  of  the  fibrous  membrane,  but  the  great  majority  of  them 
are  situated  internally  to  that  structure,  and  then  form  a  dis- 
tinct layer,  the  "glandular  layer."  They  are  most  abundant 
in  the  spaces  between  the  cartilages.  Their  ducts  pierce  the 


deb 


FIG.  109. — Transverse  section  of  bronchial  twig,  6  mm.  in  diameter :   a.  outer  fibrous  layer ;  R,  muscu- 
lar layer  ;  c,  inner  fibrous  layer  (mucosa)  ;  d.  epithelium.    Magnified  30  diameters.     F.  E.  Schulze. 

mucous  membrane  obliquely,  so  that  the  entire  length  of  a 
duct  is  not  usually  found  in  a  section  of  the  tracheal  wall. 
At  short  intervals,  between  the  columnar  cells  of  the  surface, 
other  cells  are  found,  of  a  spindle  shape,  or  somewhat  stellate. 
These  cells  send  processes  upward  to  the  surface  and  down- 
ward into  the  basilar  membrane,  where  they  become  contin- 
uous with  other  branched  cells.  The  prolongation  which  passes 
upward  to  the  surface  is  usually  single,  though  it  may  occasion- 
ally send  off  a  delicate  filamentary  branch,  which  is  lost  in 
the  cement  substance  between  adjacent  cells. 

The  process,  sometimes  double,  which  passes  downward 
connects  with  a  tissue  in  the  mucosa  which  resembles  the 
lymph  canalicular  system  of  other  parts.  It  is  made  up  of 
a  network  of  branched  cells,  or  connective-tissue  corpuscles, 
which  line  a  series  of  spaces,  that  in  turn  communicate  with 
the  lymphatic  capillaries  of  the  mucous  membrane.  Sikorsk; 
injected  a  watery  solution  of  carminate  of  ammonia  into  the 


THE    RESPIRATORY    TRACT.  259 

bronchial  tubes  of  cats  and  dogs  while  the  animals  were  liv- 
ing, and  found,  post-mortem,  that  the  carmine  had  penetrated 
through  the  interepithelial  cells  above  described  into  the  lym- 
phatic vessels  below. 

The  interepithelial  cells  have  a  small  nucleus  which  stains 
more  deeply  with  hsematoxylon  than  do  the  nuclei  of  the  ordi- 
nary epithelial  cells.  In  vertical  section  they  are  more  opaque 
than  the  epithelia,  and,  when  seen  on  the  surface  of  the  mem- 
brane, appear  as  dark  spots  among  the  ciliated  cells. 

The  lymphatic  capillaries  join  to  form  larger  trunks  which 
run  along  the  sides  of  the  bronchi  communicating  freely  with 
each  other  and  with  those  of  the  neighboring  blood-vessels. 
They  are  called  by  Klein  the  peribroncMal  lymphatics. 

Beneath  the  mucosa,  and  between  it  and  the  mucous  glands, 
are  numerous  bundles  of  yellow  elastic  tissue  having  a  longi- 
tudinal direction.  Some  of  the  bands  are  quite  thick,  particu- 
larly in  the  posterior  wall,  and  raise  the  mucous  membrane  in 
longitudinal  folds. 

The  mucous  membrane  of  the  trachea  and  bronchi  has  a 
rich  network  of  capillaries.  The  racemose  glands  are  also  sup- 
plied with  a  vascular  network  which  ramifies  in  the  fibrous  tis- 
sue by  which  they  are  surrounded.  The  natural  injection  of 
these  vessels,  which  occurs  in  cases  of  bronchitis  in  the  human 
subject,  is  often  sufficient  for  their  examination. 

The  mode  of  termination  of  the  nerves  has  not  been  ascer- 
tained. 

The  trachea  should  be  hardened  in  chromic  acid  or  Miillers 
fluid,  followed  by  alcohol.  The  sections  may  be  stained  in 
hsematoxylon.  In  order  to  preserve  the  ciliated  epithelium,  it 
is  well,  as  Professor  Rutherford  suggests,  to  cut  the  sections 
with  the  freezing  microtome.  The  lymphatics  can  be  injected 
by  puncture. 

The  smaller  bronchi  and  lungs. — Beyond  the  primary  bron- 
chi (or  first  division  of  the  trachea)  the  muscular  fibres  encircle 
the  tubes  inside  of  the  cartilaginous  and  fibrous  layer  ;  indeed, 
the  primary  divisions  show  the  first  sign  of  this  new  arrange- 
ment. The  cartilages  change  from  incomplete  rings  to  irregu- 
larly shaped  plates,  which  are  found  on  all  sides  of  the  tubes, 
but  their  microscopic  structure  remains  unaltered.  The  longi- 
tudinal elastic  fibres  are  contained  between  the  muscular  and 
mucous  coats.  The  tubes  divide  and  subdivide  generally  in  a 


260 


MANUAL    OF   HISTOLOGY. 


dichotomous  manner,  diminishing  gradually  in  calibre,  tlie 
combined  area  of  the  branches,  however,  always  exceeding  that 
of  the  trunk  from  which  they  spring.  No  change  occurs  in 
their  structure,  except  a  gradual  thinning  of  their  walls,  until 
they  reach  a  diameter  of  about  1  mm.,  when  the  cartilages 
disappear  and  the  attenuation  is  more  marked.  The  circular 
muscular  fibres  continue  to  exist,  as  also  the  longitudinal  elas- 
tic fibres,  but  the  mucous  glands  disappear.  After  a  still 
further  division  the  tubes  are  diminished  to  a  diameter  of  .20 
to  .30  mm.,  the  muscular  fibres  become  more  sparse,  and  the 
epithelium  is  reduced  to  a  single  layer  of  low,  somewhat  cubi- 
cal cells,  which  are  still  ciliated.  These  are  the  lobular  bronchi, 
each  one  going  to  a  single  pulmonary  lobule.  The  lobular 
bronchi  each  give  off  ten  to  fifteen  smaller  tubes,  known  as  the 
terminal  bronchi  or  bronchioles.  They  are  straight  and  cylin- 
drical, their  walls  are  very  thin  and 
delicate,  and  their  epithelial  cells 
gradually  lose  their  cilia  and  become 
flattened  plates.  Each  bronchiole 
leads  to  a  smaller  division  of  the  lob- 
ule, called  an  acinus  or  lobulette.1  The 
bronchioles  divide  into  short  canals, 
the  alveolar  passages,  usually  three 
for  each  acinus.  Their  walls  are  thin 
and  bulge  outward  on  all  sides,  form- 
ing, externally,  little  projections  or 
elevations;  internally,  shallow  depressions  or  cavities  which 
open  into  the  calibre  of  the  tube.  They  also  give  off  secondary 
branches,  called  infundibula,  which  have  groups  of  such  little 
cavities  attached  to,  and  opening  into  them.  The  little  cavities 
are  the  alveoli  or  air-cells  of  the  lung.  From  this  description 
it  will  be  seen  that  each  lobule  has  ten  to  fifteen  acini  or  lobu- 
lettes,  and  that  the  lobulette  is  made  up  of  alveoli  or  air-cells, 
which  open  into  common  spaces  or  infundibula,  which  in  turn 
communicate  with  the  alveolar  passages.  The  alveoli,  which 
are  connected  with  the  infundibula,  are  called  terminal  alve- 
oli ;  those  which  open  on  the  sides  of  the  alveolar  passage  are 
called  the  parietal  alveoli.  The  latter  are  called,  by  Dr.  Wa- 
ters, the  bronchial  alveoli.  The  alveolar  passages,  infundibula, 


FIG.  110.— A  system  of  alveolar  pas- 
sages with  infundibuli  from  an  ape's 
lung :  «,  terminal  bronchial  twig ;  6,  &, 
infundibula;  c,  c,  alveolar  passages. 
Magnified  10  times.  F.  E.  Schulze. 


1  Dr.  Waters  :  The  Anatomy  of  the  Human  Lung,  London,  1860. 


THE    RESPIRATORY    TRACT. 


261 


and  alveoli  have  a  flat  pavement  epithelium  resting  on  an  ap- 
parently structureless  basement-membrane.  Outside  of  this  are 
numerous  elastic  and  muscular  fibres,  curving  around  the  cavi- 
ties, and  holding  in  their  meshes  the  capillary  blood-vessels. 
The  muscular  fibres  are  very  numerous  in  the  walls,  of  the  al- 
veolar passages  and  infundibula.  The  alveoli  have  a  diameter 
of  .1  to  .4  mm.,  but  their  size  varies  greatly  according  to  the 
degree  of  inflation  of  the  lungs. 


FIG.  111.— Section  through  an  infundibnlnm  :  or,  entrance  from  the  alveolar  passage  into  the  infundi- 
bulum ;  &,  nuclei  of  smooth  muscular  cells.    Magnified  30  diameters.    F.  E.  Schulze. 

The  epithelium  in  the  alveoli  of  the  fetal  lung  is  columnar 
in  shape,  so  that  a  section  of  such  a  lung  resembles  a  section 
of  a  glandular  organ.  But  when  the  alveoli  are  distended  at 
birth,  the  cells  change  their  form.  In  transverse  sections,  either 
real  or  optical,  of  the  alveolar  walls,  the  epithelial  plates  pro- 
ject more  or  less  into  the  cavity,  according  to  the  degree  of  dis- 
tention  of  the  lung.  This  change  of  shape  undoubtedly  occurs 
during  life  with  the  alternating  expansion  and  contraction  of 
the  thorax,  and  should  be  taken  into  account  in  considering 
the  pathological  changes  of  inflammation,  collapse,  etc.  By 
injection  of  a  weak  solution  of  silver  nitrate  (^  per  cent.)  into 
the  bronchi  of  a  fresh  lung,  and  its  subsequent  immersion  in 


262 


MANUAL    OF   HISTOLOGY. 


alcohol,  the  lines  between  the  epithelial  plates  can  be  demon- 
strated.    The  nuclei  can  be  stained  with  carmine. 

Some  of  the  cells  are  converted  into  hyaline  plates.  The 
alveolar  epithelium  of  the  human  lung  is  not  so  readily  demon- 
strated as  that  of  animals,  principally  because  too  long  a  time 
usually  elapses  between  death  and  the  post-mortem  dissection. 
In  some  traumatic  cases  an  autopsy  can  be  made  early,  and  as 


FIG.  112. — Interior  of  an  alveolus.     Lung  injected  with  a  solution  of  nitrate  of  silver  to  show  the  lines 
between  the  alveolar  epithelial  cells.     F.  E.  Schulze. 

favorable  opportunity  had  of  examining  these  structures.  They 
can  be  shown  very  well  in  fresh  sections  cut  with  Valentin's 
knife. 

The  spaces  between  the  alveoli  and  acini  contain  the  elastic 
fibres  mentioned  above,  together  with  a  few  oval  connective- 
tissue  nuclei  and  muscular  elements.  The  lobules  are  held 
together  by  thin  septa  of  connective  tissue.  The  connective 
tissue  is  also  found  in  the  angles  of  division  of  the  lobular 
bronchi  and  bronchioles. 

The  muscle-cells  may  be  identified  by  their  elongated, 
fusiform  nuclei.  A  further  proof  of  their  existence  is  found 
in  certain  cases  of  cirrhosis  of  the  lung,  in  which  many  distinct 
muscular  fibres  are  found  in  the  new  connective  tissue.1 

The  branches  of  the  pulmonary  artery  follow  the  course 

1  Buhl :  Lungenentz.  Tuberculosis,  u.  Schwindsucht,  Munchen.     1873,  S.  358. 


THE    EESPIRATOEY    TRACT.  263 

of  the  bronchi  as  far  as  the  lobules.  The  lobular  branches 
are  terminal  arteries — i.e.,  they  do  not  anastomose  with  each 
other.  They  break  up  into  very  small  branches,  which  encircle 
the  alveoli  and  supply  the  capillary  plexuses  of  their  walls. 
These  capillaries  are  very  small,  and  the  network  so  fine  that, 
when  injected,  the  open  spaces  are  not  as  wide  as  the  vessels 
themselves.  This,  however,  will  vary  with  the  degree  of  dis- 
tention  of  the  lung.  Between  two  adjacent  alveoli  only  one 


PIG.  113.— Section  of  human  lung  injected  through  the  pulmonary  artery :  a,  a,  free  alveolar  margins ; 
6,  small  arterial  branch ;  c,  c,  alveolar  walls  seen  in  transverse  section.     F.  E.  Schulze. 

capillary  plexus  is  found,  the  branches  of  which  are  seen  to 
pursue  an  undulating  course,  projecting,  first,  into  the  cavity 
on  one  side,  then  into  that  on  the  other.  These  unite  again 
into  veins  which  run  irregularly  through  the  lobules  to  unite 
upon  the  bronchi  and  follow  their  course  to  the  root  of  the 
lung.  The  peculiarities  of  the  pulmonary  veins  are,  1st,  that 
their  united  calibre  does  not  exceed  (if  it  equals)  that  of  the 
arteries  ;  3d,  that  they  have  no  valves.  The  bronchial  vessels 
supply  the  coats  of  the  bronchial  tubes  and  the  surrounding 
connective  tissue  and  the  pulmonary  pleura. 

But  the  line  of  demarcation  between  the  bronchial  and  pul- 
monary circulations  is  indistinct  on  the  venous  side,  as  injec- 
tions thrown  into  the  bronchial  arteries  fill  the  pulmonary 


264  MANUAL    OF    HISTOLOGY. 

veins  and  capillary  plexuses  and  overflow  into  the  pulmonary 
arteries.1 

It  appears  from  this  that  part  of  the  blood  from  the  bron- 
chial arteries  does,  or  may,  return  through  the  pulmonary  veins. 
In  their  course  through  the  lung,  the  pulmonary  arteries  lie 
upon  the  upper  and  anterior  aspect  of  the  bronchial  tubes, 
while  the  veins  are  found  on  their  inferior  surface.  The  bron- 
chial arteries  follow  the  tubes  and  divide  with  them. 

The  lymphatics  of  the  alveolar  septa  are  a  series  of  lacunar 
spaces  lined  by  branched  connective- tissue  corpuscles,  whose 
nuclei  have  already  been  described  as  being  visible  in  ordinary 
sections  of  the  lung. 

In  sections  of  a  lung  treated  with  silver  nitrate  the  forms 
of  the  cells  are  distinguishable.  According  to  Klein  the  pro- 
cesses of  these  cells  pass  upward  between  the  epithelial  plates 
of  the  alveoli  so  as  to  bring  the  cells  into  direct  communica- 
tion with  the  cavity,  just  as  we  have  seen  the  interepithelial 
cells  of  the  bronchial  mucous  membrane  send  certain  processes 
upward  between  the  columnar  epithelia  and  others  downward 
to  the  cells  of  the  lymph  lacunae.  On  examining  the  epithelium 
of  an  alveolus,  small,  round,  dark  spaces  are  seen  between  the 
cells  ;  these  are  said  by  Klein  to  be  the  projecting  processes  of 
the  branched  cells  of  the  lymph  lacunar  system.  The  ends  of 
these  processes,  both  here  and  on  the  bronchial  mucous  mem- 
brane, are  called  pseudostomata,  in  contradistinction  to  the 
true  stomata  of  the  serous  membranes. 

The  small  spaces,  or  lacunae,  open  into  lymphatic  radicles, 
which  have  a  regular  endothelial  lining.  These  pass  inward 
toward  the  root  of  the  lung,  upon  the  bronchi  and  the  walls 
of  the  vessels.  On  the  vascular  walls  they  communicate  freely 
with  each  other,  and  at  times  completely  invest  the  vessel  with 
a  lymphatic  sheath  like  that  of  the  cerebral  vessels.  In  this 
situation  they  are  called  perivascular  lymphatics.  The  peri- 
vascular  and  peribronchial  lymphatics  communicate  freely.  At 
the  surface  of  the  lung  there  is  a  plexus  immediately  beneath 
the  pleura  (subpleural  lymphatics)  from  which  trunks  of  some 
size  run  to  the  root  of  the  lung.  They  communicate  with  the 
perivascular  system  and  with  the  pleural  cavity.  The  final 
termination  of  all  these  channels  is  in  the  bronchial  glands. 

1  Dr.  Waters. 


THE    RESPIRATORY   TRACT.  265 

The  nerves  of  the  lungs  are  derived  from  the  sympathetic 
and  pneumogastric.  Their  mode  of  termination  is  not  known. 

For  the  examination  of  the  general  structure  of  the  lung  it 
may  be  inflated  and  dried  pretty  rapidly  in  the  sun  or  by  a 
fire.  For  more  careful  examination  it  should  be  hardened  in 
chromic  acid,  Miiller's  fluid,  or  alcohol.  The  hardening  fluid 
should  be  injected  into  the  air- passages. 

In  order  to  distend  the  vesicles  it  is  well,  before  placing  the 
lung  iri  the  hardening  fluid,  to  inject  the  bronchi  with  simple 
gelatine.  The  vessels  may  also  be  injected  with  a  colored 
mass.  The  lungs  of  the  lower  animals  are  used  for  these 
demonstrations,  owing  to  the  difficulty  of  obtaining  normal 
human  lungs  in  a  perfectly  fresh  condition.  The  investigation 
of  the  lymphatics  is  attended  with  great  difficulty.  They  may 
be  demonstrated  by  the  puncture  method.  Klein  found  that 
on  injecting  the  blood-vessels,  under  high  pressure,  with  Ber- 
lin blue  or  silver  nitrate,  some  of  the  capillaries  ruptured,  and 
the  fluid  passed  into  the  perivascular  lymphatics. 

The  pleura. — The  pleura,  like  the  other  serous  membranes, 
consists  of  a  connective-tissue  ground-substance  covered  by  a 
single  layer  of  polygonal  endothelial  cells.  In  the  costal  pleura 
the  subserous  connective  tissue  is  more  abundant,  and  its  at- 
tachment to  the  thoracic  wall  is  not  so  firm  as  is  that  of  the 
pulmonary  pleura  to  the  lung.  The  structure  of  the  pleura  is 
most  conveniently  studied  in  the  smaller  mammals.  It  can 
also  be  demonstrated  in  young  children. 

To  demonstrate  the  endothelium  of  the  surface,  the  thorax 
of  a  recently  killed  animal  should  be  opened,  care  being  taken 
not  to  rub  or  otherwise  injure  the  pleura.  The  surfaces  are  to 
be  washed  by  pouring  distilled  water  over  them,  in  order  to 
remove  the  serum,  and  then  a  weak  solution  of  silver  nitrate 
(4 — I  per  cent.)  allowed  to  flow  over  them.  After  a  few  mo- 
ments the  surfaces  are  bathed  with  pure  water.  The  diaphragm- 
atic or  mediastinal  portion  is  then  excised  with  scissors, 
immersed  in  distilled  water  or  glycerine,  and  exposed  to  the 
daylight  until  it  takes  a  light  reddish-brown  color.  It  may 
now  be  floated  on  to  a  slide,  carefully  smoothed  by  traction  at 
the  edges,  and  mounted  in  glycerine.  The  portion  excised 
should  be  large,  so  that  it  can  be  manipulated  without  touch- 
ing the  part  which  is  to  be  examined.  For  this  reason  it  is  well 
to  take  with  it  some  of  the  surrounding  structures,  e.g.,  the 


266  MANUAL    OF    HISTOLOGY. 

entire  diaphragm,  with  the  mediastinal  portion,  together  with 
the  heart  and  pericardium. 

It  will  be  seen  that  the  endothelium  is  composed  of  a  great 
number  of  polygonal  plates  whose  edges  are  glued  together  by 
a  substance  which  has  been  stained  brown  or  black  by  the  sil- 
ver. Nuclei  are  seen  in  many  of  them,  or  they  can  be  shown 
by  staining  with  carmine  or  hsematoxylon.  Small  openings 
are  to  be  seen  in  certain  localities  surrounded  by  cells  of  a 
more  cubical  form,  with  large,  distinct  nuclei.  In  other  places 
small  dark  spots  are  seen  between  the  cells.  The  openings  are 
known  as  stomata,  and  communicate  with  lymphatic  vessels 
running  beneath  the  endothelium.  The  dark  spots  &YQ  pseudo- 
stomata,  and  are  similar  in  their  nature  to  the  pseudo-stomata 
of  the  alveoli  and  bronchial  mucous  membrane ;  i.e.,  they  are 
the  ends  of  processes  of  the  branched  cells  of  the  ground-sub- 
stance reaching  up  between  the  endothelial  plates.  In  order 
to  demonstrate  the  ground- sub  stance  or  connective-tissue  layer 
of  the  pleura,  the  fresh  surface  is  carefully  pencilled  with  a 
soft  brush  dipped  in  the  fluid  of  the  abdominal  cavity,  or  in 
artificial  serum.  After  washing  with  distilled  water,  the  solu- 
tion of  silver  nitrate  is  poured  over  it,  and  it  is  treated  as  be- 
fore. On  examination,  the  branched  connective-tissue  cells 
are  seen  communicating  with  each  other  by  their  processes. 

Blood-vessels  and  lymphatics  are  also  seen,  and  in  a  favor- 
able place  the  endothelium  of  the  latter  is  seen  to  be  continuous 
with  the  branched  cells.  These  cells  line  the  cavities  of  the 
connective  tissue,  and  belong  to  the  lymph  lacunar  system. 

The  lymphatic  vessels  accompany  the  blood-vessels,  some- 
times ensheathing  them.  They  are  identified  by  the  shape  of 
their  endothelial  cells,  which  are  wider  and  more  polygonal  in 
form  than  those  of  the  veins.  It  will  be  seen  from  this  descrip- 
tion that  the  serous  membrane  is  a  lymphatic  structure.  Its 
cavity  communicates  by  means  of  the  stomata  with  the  lym- 
phatic vessels  below,  while,  by  means  of  the  pseudo-stomata, 
it  communicates  with  the  lacunar  spaces  which  are  lined  by 
the  branched  cells.  To  demonstrate  the  pulmonary  pleura, 
the  lungs  should  be  excised,  moderately  distended  with  air 
(which  is  retained  in  them  by  ligature  of  the  trachea),  treated 
with  silver  nitrate,  as  already  described,  and  then  immersed  in 
alcohol.  After  a  few  days  sections  are  made  parallel  to  the 
surface. 


THE    RESPIRATORY    TRACT.  267 

If  the  lung  be  pencilled  before  it  is  treated  with  the  silver 
solution  the  deeper  structures  can  be  examined.  The  sections 
should  be  mounted  in  glycerine  with  the  external  surface 
upward.  The  appearances  here  are  similar  to  those  already 
described.  The  capillary  ]ymphatic-vessels  communicate  with 
the  superficial  pulmonary  branches  forming  the  subpleural 
lymphatics. 

The  endothelial  cells  of  the  pulmonary  pleura  vary  in 
shape  according  to  the  degree  of  distention  of  the  lung.  In 
the  lung  which  has  been  inflated  before  hardening,  the  cells 
appear  as  flat  plates,  but  in  the  atelectatic  lung  of  a  foetus,  or 
the  collapsed  lung  of  an  animal  that  has  breathed,  they  are 
cubical  or  even  columnar  in  shape.  This  difference  is  most 
marked  in  the  guinea-pig,  owing  to  the  presence  of  a  layer  of 
muscular-fibres  beneath  the  pleura  of  that  animal.  The  tops 
of  the  cells  which  have  this  pyramidal  shape  are  not  flat  as  in 
true  columnar  epithelium,  but  rounded.  This  change  of  shape 
simply  indicates  that  the  cells  accommodate  themselves  to 
changes  of  space.  These  changes,  in  a  lesser  degree,  must  be 
occurring  constantly  during  life,  with  the  movements  of  respi- 
ration. On  the  costal  pleura,  the  stomata  are  only  found  in 
the  intercostal  spaces. 

Attached  to  the  lower  border  of  the  lung  are  minute  ap- 
pendages, the  "pleural  appendages"  forming  a  sort  of  fringe 
connected  with  the  pleura.  Some  are  visible  to  the  naked 
eye,  some  microscopic.  The  larger  are  made  up  of  connective 
tissue  and  blood-vessels,  and,  exceptionally,  nervous  fibres  in 
the  larger  ones.  They  are  covered  by  round  cells,  sometimes 
resembling  epithelium.  The  smallest  ones  are  structureless, 
and  in  general  have  no  epithelial  covering.1 


BIBLIOGRAPHY. 

COYNE,  P.  Recherches  sur  1'anatomie  normale  de  la  muqueuse  du  Larynx.  Ar- 
chives de  Physiologic,  p.  92.  Paris,  1874. 

STIRLING.  Nervous  Apparatus  of  the  Lung.  Brit.  Med.  Journal.  Vol.  II.,  p.  401. 
1876. 

CADIAT.  Des  rapports  entre  le  develop,  du  poumon  et  la  structure.  Jour,  de 
1'anat.  et  de  la  Phys.,  No.  6,  p.  591.  1877.  And,  Structure  et  devel.  du 
poumon.  Gaz.  Med.  de  Paris,  No.  17,  p.  214.  1877. 

1  Luschka :  Anatomic  des  Menschen,  Bd.  I.,  S.  298. 


268 


MANUAL    OF    HISTOLOGY. 


GRANCHER.     Note  sur  lea  lymphat.  du  poumon.     Gaz.  Med.  de  Paris,  No.  9,  p.  103. 

1877. 
AEBY.     Die   Gestalt  d.    Bronchialbaumes  u.    die  Homol.    d.    Lungenlappen  beira 

Menschen.     Med.  Centralbl.,  No.  16,  p.  290.     1878. 
SEILER,  C.     Researches  on  the  Anatomy  of  the  Vocal  Cords.     St.  Louis  Med.  and 

Surg.  Journal,  p.  333.    April  5,  1880.    And,  Minute  Anatomy  of  the  Larynx, 

Normal  and  Pathological.     Archives  of  Laryngology.     Vol.  L,  Nos.  1  and  2, 

and  to  be  continued.     1880. 


CHAPTER  XVIII. 

THE   SKIN. 

BY  A.  R  ROBINSON,  M.D., 

Lecturer  on  Normal  Histology  in  the  Bellevue  Hospital  Medical  College,  New  York. 

General  plan  of  arrangement. — The  integumentum  commu- 
ne, or  skin,  forms  the  external  covering  of  the  body,  which 
it  mechanically  protects,  and  at  the  same  time  is  endowed 
with  certain  physiological  functions.  The  surface  of  the  skin 
in  some  parts  of  the  body  is  smooth  and  soft ;  in  others  it 
is  more  or  less  uneven  and  rough.  This  latter  condition 
depends  upon  the  presence  of  pores,  hairs,  furrows,  and 
ridges.  The  pores  correspond  to  the  surface  openings  of  the 
hair-follicles,  sebaceous  and  sweat-glands.  The  hairs  vary 
in  amount  of  development  according  to  their  situation.  In 
the  so-called  hairy  regions  they  are  largest ;  other  parts  are 
provided  only  with  a  soft  down  (lanugo  hairs).  There  are 
no  hairs  on  the  palms  of  the  hands  and  soles  of  the  feet,  the 
dorsal  surfaces  of  the  terminal  phalanges  of  the  fingers  and  toes, 
the  glans  penis,  and  inner  surface  of  the  prepuce.  The  fur- 
rows are  either  long  and  deep,  or  short  and  superficial.  The 
former  are  chiefly  found  in  the  flexures  of  the  joints,  and  cor- 
respond to  the  folds  in  the  derma  produced  by  movements  of 
the  joint.  The  latter  run  between  the  papillary  elevations, 
and,  by  crossing  each  other,  divide  the  surface  into  a  number 
of  polygonal  or  lozenge- shaped  fields.  This  division  is  well- 
marked  on  the  backs  of  the  hands.  These  superficial  furrows 
are  more  developed  on  the  extensor  than  on  the  flexor  surfaces 
of  the  extremities,  and  in  the  lumbar  region  more  than  on  the 
anterior  surface  of  the  abdomen.  Their  direction  is  dependent 
on  the  degree  of  the  tension  of  the  skin.  The  ridges  correspond 
to  the  papillae,  and  are  most  developed  on  the  palmar  surfaces 
of  the  last  digital  phalanges.  The  color  of  the  skin  varies  in 


270 


MANUAL    OF    HISTOLOGY. 


individuals  according  to  race,  and  in  the  same  individual  ac- 
cording to  the  part  of  the  body.  The  dark  skin  of  some  races 
depends  upon  the  presence  of  pigment  in  the  cells  of  the  rete 
Malpighii.  In  the  white  race,  dark  pigment  is  usually  pres- 
ent in  greatest  quantity  in  the  areolse  of  the  nipples  and  in 
the  scrotum  and  labise. 

General  structure. — The  skin  is  composed  of  the  follow^ 
ing  parts :  epidermis,  corium,  subcutaneous  connective  tissue, 


-.-.* 


e 


FIG.  114. — Diagrammatic  perpendicular  section  through  the  normal  skin :  a,  epidermis ;  b,  rete  Mal- 
pighii; c,  papillary  layer;  d,  corium;  e,  panniculus  adiposus;  /,  spirally  bent  end  of  excretory  sweat- 
dnct ;  (7,  straight  portion  of  excretory  duct  of  sweat-gland  ;  A,  coil  of  sweat-duct ;  »',  hair-shaft ;  *,  root 
of  hair ;  /,  sebaceous  gland.  After  Neumann. 

blood-vessels,  nerves,  lymphatics,  sweat  and  sebaceous  glands, 
hairs,  and  nails. 

A  perpendicular  section  through  the  skin  shows  (Fig.  114) 
three  well-marked  layers ;  the  most  superficial  is  called  the 
epidermis  proper,  a,  b  ;  the  middle  layer  is  the  corium  or  cutis, 
d  ;  and  the  deepest  layer  the  subcutaneous  connective  tissue,  e. 
The  limit  of  the  epidermis  at  its  place  of  union  with  the  corium 
is  sharply  defined,  but  the  corium  and  subcutaneous  connec- 


THE    SKIN".  271 

live  tissue  gradually  merge  into  eacli  other,  the  boundary  be- 
tween them  being  only  an  artificial  one. 

Commencing  with  the  epidermis,  we  will  describe  in  detail 
the  minute  structure  of  the  different  tissues  and  organs  of  the 
skin,  omitting  only  the  lymphatics. 

Description  of  the  different  layers.—  The  epidermis  is 
generally  subdivided  into  several  layers,  with  specially  distinc- 
tive names  for  each  layer ;  but  though  such  a  division  has 
some  practical  value,  histologically  it 
is  incorrect,  as  the  cells  of  the  lowest 
layer  are  transformed,  at  some  period 
of  their  existence,  in  their  movement 
toward  the  free  surface,  into  the  cells 
of  the  other  layers.  Examination  with 
high  powers  also  shows  that  the  chan- 
ges in  the  molecular  constitution  or 
chemical  condition  of  the  cells  of  the 
epidermis  —  changes  which  produce 
differences  in  their  appearance  —  are  • 

quite  gradual.  Consequently,  sharply  defined  layers  are  not 
found.  For  practical  reasons,  however,  it  is  well  to  adopt  the 
usual  classification.  In  Fig.  115  these  layers  are  shown. 

Another  division  is  into  Malpighian  and  corneous  layers 
only,  the  former  comprising  the  rete  and  the  granular  layer, 
and  the  latter  the  stratum  lucidum  and  corneous  layer.  The 
Malpighian  layer,  as  compared  with  the  corneous  layer,  pre- 
sents a  more  or  less  dark,  granular  appearance,  while  the  latter 
is  homogeneous,  and  its  cells  have  a  lamellar  arrangement. 

The  rete  MalpigMi  consists  of  nucleated  corpuscles,  rich  in 
protoplasm,  granular  in  appearance,  and  disposed  more  or  less 
in  parallel  strata,  the  elements  of  the  different  layers  differing 
somewhat  from  each  other  as  regards  their  size  and  shape.  The 
lowest  layer  consists  of  columnar-shaped  cells  arranged  pali- 
sade-like, with  their  long  axes  more  or  less  perpendicular  to  the 
surface  of  the  corium.  Where  the  papillae  are  well  developed, 
this  perpendicular  arrangement  is  not  so  marked.  The  base  of 
some  of  these  bodies  terminates  in  a  pointed  extremity,  which 
passes  a  short  distance  into  the  underlying  corium.  Each  of 
them  has  an  oval  nucleus.  The  cell-body  consists  of  a  small 
quantity  of  slightly  granular,  shining  protoplasm.  The  cor- 
puscles of  this  layer  are  not  united  to  each  other  by  bands,  as 


272  MANUAL    OF   HISTOLOGY. 

in  the  other  layers.  The  next  two  or  three  strata  consist  of 
more  or  less  polygonal-shaped  bodies,  each  with  a  spherical 
nucleus.  The  cells  of  these  layers  are  large,  their  contours 
sharply  defined,  and  they  contain  more  or  less  pigment.  It  is 
this  substance  deposited  in  the  corpuscles  that  gives  the  charac- 
teristic color  to  the  different  races  of  mankind.  Their  cell-bod- 
ies are  larger  in  proportion  to  the  nucleus  than  in  the  first  layer. 
In  the  succeeding  laj^ers  the  cells  increase  in  size  and  are  more 
granular  in  appearance,  the  cells  and  nuclei  become  flatter  as 
they  approach  the  granular  layer,  and,  finally,  lie  with  their  long 
axes  parallel  to  the  surface.  The  granular  structure  which  in 
the  lowest  layer  is  most  marked  around  the  nucleus,  gradu- 
ally extends  toward  the  margin  of  the  cells,  as  the  surface  is 
approached,  so  that  finally  a  clear  area  is  seen  around  the 
nucleus,  whilst  the  remainder  of  the  cell-body  is  markedly 
granular.  At  the  same  time  the  cell-body  becomes  firmer  and 
the  nucleus  smaller. 

All  the  cells  of  the  rete  Malpighii,  except  those  of  the  first 
row,  are  united  to  each  other  by  filaments  (Martin,  Bizzozero, 
Heitzmann),  the  so-called  prickles  of  Max 
Schultze  (Fig.  116).  These  uniting  filaments 
or  bands  vary  much  as  regards  their  size 
and  length  in  different  parts  of  the  bod}'. 
They  are  most  distinct  wherever  the  Mal- 
pighian  layer  is  well  developed,  but  are 
thicker  and  longer  in  the  lower  rows  of 
ceiis  cells  than  in  the  upper.  At  the  stratum 
of  the  rete.  x  1600.  lucidum  they  cease  to  exist.  Between 

neighboring  corpuscles  the  length  of  these  bands  is  in  direct 
proportion  to  the  distance  between  the  borders  of  the  cell- 
bodies.  Hence,  where  three  or  four  cells  meet  at  one  place, 
as  in  the  centre  of  Fig.  116,  the  minute  filaments  are  much 
longer  than  those  uniting  the  bodies  of  closely  adjoining  cells. 
Examining  these  prickle-cells  with  the  microscope,  alternate 
dark  and  light  bands  are  seen  between  the  cell-borders.  With 
a  low  power,  these  light  bands  appear  to  consist  of  spaces  be- 
tween the  connecting  filaments,  the  dark  lines  being  the  con- 
necting filaments,  but  with  a  high  power  the  latter  can  be 
recognized  as  spaces  between  the  former.  The  light  bands 
can  be  traced  from  the  surface  of  one  cell  to  the  surface  of 
another,  whilst  the  dark  lines  are  the  spaces  between  these 


THE   SKIN.  273 

bands.  These  connecting  cords  sometimes  divide  and  anas- 
tomose with  each  other,  forming  a  sort  of  network  between  the 
cells.  In  this  case,  the  dark  spaces  do  not  always  extend 
from  one  cell-body  to  another,  since  they  may  correspond  to 
the  space  between  anastomosing  filaments.  These  bands  are 
therefore  not  the  prickles  of  adjoining  cells,  which  interlock 
with  each  other,  but  are  true  connecting  filaments  between 
cells  of  a  common  origin,  and  which  iiave  not  yet  become  sepa- 
rated from  each  other.  The  connecting  bands  or  fibres  gradu- 
ally diminish  in  length  and  thickness  from  below  upward,  and 
finally  cease  to  exist  when  the  granular  layer  is  reached. 

The  spaces  between  the  bands  are  filled  with  an  inter- 
cellular albuminous  substance,  and  they  may  be  regarded  as 
minute  channels  for  the  conveyance  of  nutriment  to  the  cells 
of  the  epidermis.  The  above  view  of  the  " prickles"  corre- 
sponds very  closely  with  that  held  by  Dr.  Martin,  and  differs 
from  that  of  later  observers,  who  maintain  that  the  dark  lines 
are  connecting  bands,  and  the  light  lines  the  spaces  between 
them. 

Owing  to  the  close  union  of  the  Malpighian  elements  it  is 
very  difficult  to  isolate  them.  Perhaps  the  best  way  to  accom- 
plish this  result  is  by  long  immersion  in  iodized  serum.  Fig. 
117  represents  a  cell  isolated  in  this  manner.  Here 
the  bands  have  been  torn  apart  and  the  cell-surface  is 
studded  with  thorn-like  projections.  Hardening  in 
chromic  acid,  with  subsequent  boiling  in  a  moderately 
strong  solution  of  potash,  causes  a  separation  of  the 
mucous  layer  from  the  corium  and  a  falling  apart  of  the  rete 
cells  (Biesiadecki).  The  structure  of  the  corpuscles,  however, 
can  be  best  studied  when  their  normal  relations  with  each 
other  are  preserved.  Yariations  in  the  number  of  cellular  lay- 
ers are  of  normal  occurrence  in  the  rete,  although  this  portion 
of  the  skin  shows  the  least  variation  as  regards  its  thickness. 
The  arrangement  of  the  elements  in  these  different  strata  is  the 
same  in  all  parts  of  the  body,  and  appears  to  be  independent 
of  the  thickness  of  this  layer. 

As  regards  the  direction  of  the  long  axes  of  the  cells  there 
is  a  gradual  passing  from  the  perpendicularly  seated  cells  of 
the  first  layer  to  the  horizontally  lying  cells  of  the  uppermost 
>w.  The  lower  surface  of  the  rete  adapts  itself  to  the  upper 
mrface  of  the  corium,  and  between  the  papillae  projects  down- 


274 


MANUAL    OF   HISTOLOGY. 


PIG.  118. — Horizontal  section  of  skin  through  a 
papilla.  The  migrating  cells  are  observed  as  dark 
bands  between  the  epithelial  cells  and  amongst  the 
connective  tissue  of  the  papilla.  Pagenstecher. 


ward  and  forms  the  interpapillary  rete  Malpigliii.  Wandering 
lymphoid  cells  are  frequently  present  in  the  rete.  They  are 
especially  numerous  in  some  pathological  conditions.  They 
(Fig.  118)  are  elongated  spindle-shaped  bodies  lying  between 
the  rete  cells,  and  sending  out  minute  processes.  They  color 

deeply  in  carmine,  have  a 
small  nucleus,  and  are  most 
numerous  in  the  lower  part 
of  the  rete  mucosum. 

The  granular  layer  (Fig. 
115,  b)  consists  of  one  or  two 
strata  of  flattened,  granular- 
looking  bodies,  which,  in 
perpendicular  section  appear 
spindle  -  shaped,  with  their 
long  diameter  parallel  to  the 
free  surface  of  the  epidermis. 
In  this  stratum  the  cells  are 
no  longer  connected  with  each 
other  by  bands,  as  in  the  pre- 
ceding layer.  The  nuclei  of 
these  corpuscles  are  very  distinct,  and  flattened  in  the  same 
direction  as  the  cell-body.  The  latter  has  a  very  coarsely  gran- 
ular appearance,  which  is  most  marked  near  the  nucleus,  and 
gradually  diminishes  in  degree  as  the  periphery  of  the  cell  is 
approached.  The  structure  of  these  bodies  is  best  shown  with 
hsematoxylon. 

The  stratum  lucidum,  also  called  the  stratum  of  Oehl,  is 
composed  of  at  least  three  layers  (Fig.  115,  c).  It  presents  a 
clear,  homogeneous,  or  striated  appearance.  Within  the  flat- 
tened cells  composing  it,  a  staff-shaped  nucleus  is  found.  The 
cells  of  this  layer  are  formed  from  those  of  the  granular  stra- 
tum. In  their  movement  to  the  free  surface  the  latter  become 
less  granular  and  the  inter-granular  substance  grows  more  trans- 
parent and  shining  (Unna).  This  change  from  a  granular  to  a 
homogeneous  translucent  appearance  commences  around  the 
nucleus,  whence  it  gradually  extends  to  the  periphery  of  the 
cell.  The  nucleus,  also,  usually  becomes  invisible. 

In  vertical  section  the  corneous  layer  appears  (Fig.  115,  d) 
to  be  composed  of  wavy  fibres  and  horny,  transparent  cells 
of  various  sizes  and  shapes.  This  variation  in  bulk  and  form 


THE    SKIN.  275 

depends  in  great  measure  upon  the  thickness  of  the  layer. 
The  nearer  we  approach  to  the  stratum  lucidum,  the  more  dis- 
tinct are  the  cells.  If  the  layer  is  very  thin  the  cells  appear 
as  elongated,  flat,  or  curved  bodies,  giving  to  this  part  of  the 
epidermis  a  fibrous  appearance.  When  the  corneous  stratum 
is  thick  these  cells  present  various  forms  and  sizes.  The  cor- 
puscles of  the  lower  layers  color  slightly  in  carmine,  are  poly- 
gonal or  spindle-shaped,  and  frequently  contain  a  shrivelled 
nucleus.  As  the  surface  is  approached  they  grow  flatter  and 
drier,  are  more  bent  upon  themselves,  and  color  less  and  less  in 
carmine.  The  nucleus  also  becomes  invisible.  The  most  su- 
perficial layers  are  composed  of  elongated,  flat,  dried-up  cells, 
the  so-called  epidermic  scales.  These  bodies  are  best  studied 
after  they  have  been  subjected  to  the  action  of  liquor  potassse, 
which  ca-uses  them  to  swell  up. 

The  corpuscles  of  the  stratum  corneum  are  arranged  in  lay- 
ers as  in  the  other  parts  of  the  epidermis,  but  the  elements 
forming  a  layer  are  more  closely  united  with  each  other  than 
with  those  of  the  adjoining  layers.  Hence  this  stratum  can  be 
separated  into  lamellae,  as  occurs  in  some  pathological  states 
of  the  skin.  It  accompanies,  for  example,  the  formation  of 
some  vesicles,  where  the  exuded  liquid,  prevented  from  pass- 
ing toward  the  surface,  accumulates  between  the  layers,  and 
thus  separates  them  from  each  other. 

The  corneous  layer  participates  in  the  elevations  and  de- 
pressions of  the  underlying  layers.  This  causes  the  undulat- 
ing or  wavy  appearance  of  the  lamellae,  as  observed  in  sections 
where  the  papillae  are  well  developed.  It  varies  greatly  in 
thickness  in  different  parts  of  the  body,  and  reaches  its  great- 
est development  on  the  palms  of  the  hands  and  soles  of  the  feet. 
Its  thickness  does  not  depend  upon  the  rete  Malpighii,  as  it 
sometimes  forms  a  thin  layer  where  the  rete  is  thick,  and  vice 
versa. 

The  subcutaneous  connective-tissue  layer  of  the  skin  con- 
sists principally  of  connective-tissue  bundles,  which,  coming 
from  the  underlying  fasciae  of  the  muscles  or  from  the  peri- 
osteum, pass  in  an  oblique  direction  to  the  corium.  These 
fasciculi  are  generally  cylindrical  in  form,  and  variable  in  size  ; 
by  their  anastomoses  or  divisions  they  form  larger  or  smaller 
networks,  with  correspondingly  large  or  small  interfascicular 
spaces.  Generally  large  bundles  anastomose  with  each  other 


276  MANUAL    OF   HISTOLOGY. 

in  this  layer,  and  hence  a  loose  connective  tissue  is  formed. 
Within  this  layer  adipose  tissue  is  found  in  greater  or  less 
quantity.  The  'fat-cells  are  collected  into  masses  or  lobules,  the 
number  of  cells  which  form  a  lobule  varying  greatly  in  num- 
ber. Each  of  these  latter  may  be  regarded  as  a  fat-gland,  as  it 
is  provided  with  an  afferent  artery,  a  capillary  plexus  between 
the  corpuscles,  and  one  or  more  efferent  veins.  Several  lobules 
are  sometimes  united  together  in  the  form  of  an  acinous-like 
gland,  and  are  likewise  seen  to  be  surrounded  by  a  general 
sheath  of  connective  tissue.  The  individual  fat-cells  are  round, 
flattened,  polyhedral,  or  oval-shaped,  the  form  depending  upon 
the  degree  and  direction  of  the  pressure  exerted  upon  them. 
Owing  to  the  amount  of  fat-tissue  so  often  found  in  this  layer, 
it  has  been  called  the  panniculus  adiposus.  Such  fat-lobules 
are  absent  in  the  penis,  scrotum,  labise  minorse,  eyelids,  and 
pinna.  The  corresponding  spaces  in  these  regions  are  tra- 
versed by  fine  connective- tissue  bands  or  single  fibrils.  From 
this  adipose  tissue  fat-columns  pass  upward  in  a  somewhat 
oblique  direction  to  the  bases  of  the  hair-follicles,  especially 
to  those  of  the  fine  hairs.  Their  long  axes  form  a  slight  angle 
with  the  axes  of  the  follicles,  and  they  are  nearly  parallel  to 
the  erector  pili  muscles  (Warren).  In  cases  of  starvation,  in 
the  so-called  wasting  diseases,  and  in  all  acute  diseases  at- 
tended with  excessive  loss  of  tissue,  the  fat-cells  disappear  to 
a  greater  or  less  extent.  The  skin,  in  such  instances,  becomes 
correspondingly  flaccid  and  wrinkled.  Adipose  tissue  gives  to 
the  skin  its  tension  and  fulness,  and  to  the  body  its  appear- 
ance of  roundness  or  plumpness.  Obesity  consists  in  an  exces- 
sive production  of  fat-cells. 

The  interfascicular  spaces  differ  in  size  in  proportion  to  the 
amount  of  lymph  present,  and  to  the  closeness  of  the  anasto- 
moses between  the  bundles.  In  oedema  the  lymph-spaces  are 
increased  in  size  proportionately  to  the  increased  amount  of 
liquid  present.  The  interfascicular  spaces  all  communicate 
with  each  other,  as  is  shown  by  the  rapidity  with  which  a 
hypodermically  injected  liquid  can  be  dispersed  by  manipu- 
lation. 

The  connective-tissue  cells  of  this  layer  and  of  the  corium 
consist  of  branched  cells  (Ravogli)  which  surround  the  white 
fibrous  bundles  and  send  in  processes  between  the  fibres.  Ac- 
cording to  some  observers,  these  cells  are  epithelioid  in  charac- 


THE    SKIN.  277 

ter.  The  elastic-tissue  fibres  are  developed  from  the  processes 
of  the  branched  cells. 

Besides  connective-tissue  fibres  and  cells,  lympJioid  corpus- 
cles are  present  in  this  layer.  They  exist  in  greatest  number 
near  the  blood-vessels  and  glands.  In  this  situation  they  are 
of  a  roundish  form,  but  in  the  parts  distant  from  the  blood- 
vessels they  are  more  or  less  spindle-shaped,  and  are  to  be 
regarded  as  wandering  cells. 

The  convoluted  part  of  the  sweat-glands  and  the  lower  part 
of  the  hair-follicles  of  deep-seated  hairs  lie  in  this  layer. 

Blood-vessels,  lymphatics,  and  nerves  are  present.  The 
blood-vessels  are  large,  and  after  giving  off  small  branches  to 
the  hair- follicles,  sweat-glands,  and  fat-lobules,  pass  upward 
to  the  corium. 

Pacinian  corpuscles  are  found  in  connection  with  some  of 
the  nerves.  For  a  description  of  these  bodies  the  reader  is  re- 
ferred to  the  article  on  the  nerves. 

The  principal  part  of  the  corium  consists  of  white  fibrous  and 
elastic  tissue,  the  latter  increasing  in  amount  with  advancing 
age.  Here  the  white  fibrous  tissue  forms  a  much  denser,  firmer 
structure  than  in  the  previous  layer.  It  consists  of  deep 
oblique,  and  superficial  horizontal  bundles.  The  latter  com- 
prise fine  bundles  of  connective  tissue  which  run  parallel  with 
the  surface  of  the  skin,  and  by  their  division  and  anastomoses 
form  a  very  fine  network  with  small  interfascicular  spaces. 
From  this  layer  bundles  pass  upward  into  the  papillae,  and 
these  form  a  second  denser  network.  The  deeper  layer  is 
formed  by  a  continuation  upward  of  the  subcutaneous  con- 
nective-tissue bundles.  These  pass  upward  in  an  oblique  direc- 
tion, and  as  they  reach  the  corium  divide  into  fasciculi.  Here 
they  continue  to  divide  and  anastomose  with  each  other  and 
with  fibres  from  the  horizontally  running  bundles.  The  anas- 
tomoses are  very  close  ;  hence,  the  corium  is  formed  of  a  dense 
network  of  connective  tissue,  except  in  those  parts  which  are 
traversed  by  blood-vessels,  lymphatic  vessels,  nerves,  hair-folli- 
cles, and  sebaceous  and  sweat  glands.  Immediately  around 
the  hair-follicles,  sweat-ducts,  and  sebaceous  glands  the  con- 
nective tissue  is  dense,  and  the  fibres  run  parallel  with  the  di; 
rection  of  the  organs.  Owing  to  the  greater  size  of  the  connec- 
tive-tissue bundles  in  the  lower  part  of  the  corium,  and  the 
consequent  looseness  of  the  network  formed  by  their  anasto- 


278  MANUAL    OF    HISTOLOGY. 

moses,  this  part  of  the  corium  lias  been  called  the  pars  reticu- 
laris  corn,  in  contradistinction  from  the  finer  network  formed 
in  the  upper  part,  to  which  the  name  pars  papillarls  has  been 
applied.  But  neither  between  these  two  parts  nor  between  the 
subcutaneous  layer  and  the  corium  is  there  any  sharp  dividing 
line,  the  transition  being  a  gradual  one. 

As  already  mentioned,  the  size  of  the  interfascicular  spaces 
depends  upon  the  closeness  of  the  anastomosis  between  the 
bundles  and  fibres.  The  direction  of  the  bundles  corresponds 
with  that  taken  by  the  blood-vessels. 

The  connective-tissue  corpuscles  of  the  corium  resemble 
those  found  in  the  subcutaneous  layer,  and  also  bear  the  same 
relation  to  its  connective-tissue  bundles.  From  the  upper 
portion  of  the  corium  fibres  pass  upward  to  make  the  papillae. 
The  form  of  the  papillae  is  very  variable  in  different  parts  of 
the  body.  Where  they  are  most  developed,  as  on  the  inner 
surface  of  the  terminal  phalanges  of  the  fingers  and  toes,  they 
are  conical  in  shape.  In  some  other  regions  they  form  only 
slight  elevations  on  the  corium,  giving  a  wave-like  appearance 
to  its  upper  surface.  They  consist  of  a  close  network  of  white, 
fibrous  connective  tissue  combined,  especially  in  the  central 
part  of  the  papilla,  with  a  large  number  of  elastic  fibres.  Those 
papillae  which  contain  tactile  corpuscles  are  called  nerve-pa- 
pillae. 

The  corium  is  separated  from  the  stratum  mucosum  by  a 
thin,  transparent  basement-membrane,  containing  oval  nuclei. 
Its  under  surface  is  not  sharply  defined,  and  from  it  prolonga- 
tions pass  upward  between  the  cylindrical  cells  of  the  rete, 
giving  this  surface  a  notched  appearance  similar  to  that  ob- 
served on  the  inner  margin  of  the  internal  sheath  of  the  hair- 
follicle. 

Elastic  fibres  are  present  in  large  numbers  in  the  corium, 
especially  in  its  upper  part,  where  they  form  a  network  around 
and  between  the  white  fibrous  tissue-bundles.  In  the  lower 
part  of  the  corium  they  form  a  large  network,  which  becomes 
finer  as  the  surface  is  approached.  The  number  of  elastic 
fibres  increases  with  advancing  years.  With  this  increase  of 
elastic  fibres  there  is  a  corresponding  decrease  of  the  white 
fibrous  connective-tissue  cells  (Ravogli).  Numerous  wander- 
ing cells  are  met  with  in  the  corium,  especially  in  the  vicinity 
of  the  blood-vessels  and  glands.  Hair-follicles,  sebaceous 


THE    SKIN.  279 

glands,  sweat-ducts,  nerves,  lymphatic  vessels,  and  non-striated 
muscles  are  also  present  in  this  layer.  For  a  fuller  descrip- 
tion of  the  intimate  structure  of  the  connective-tissue  bundles 
and  cells,  see  the  subject  of  connective  tissues. 

Blood-vessels. — Only  the  corium  and  subcutaneous  tissue 
are  provided  with  blood-vessels.  The  arterial  blood-vessels 
supplying  the  skin  form  two  parallel  horizontal  layers,  a  su- 
perficial and  a  deep  one.  The  deep  layer  lies  in  the  subcuta- 
neous tissue,  and  consists  of  large  vessels  running  parallel  to 
the  general  surface.  From  this  horizontally  lying  deep  layer, 
branches  are  distributed  to  the  sweat-glands  and  fat-follicles  of 
this  region.  The  principal  branches,  however,  pass  perpendicu- 
larly or  obliquely  upward  through  the  corium  to  its  upper  part, 
and  form  immediately  beneath  the  papillae  (after  free  branch- 
ing and  anastomosis)  a  superficial  horizontal  layer,  the  stratum 
subpapillare.  From  the  vessels  ascending 
through  the  corium  branches  are  given  off  to 
the  hair-follicles,  sebaceous  glands,  and  gen- 
eral tissue  of  the  corium.  From  the  stratum 
subpapillare  small  branches  pass  upward  into 
the  papillse,  where  they  become  capillary  ves- 
sels,  which  proceed  to  the  summit  of  the 
papilla.  (See  Fig.  119.)  Before  reaching  this  point,  however, 
they  frequently  divide  into  two  or  more  branches.  Frequently, 
those  papillse  in  which  tactile  corpuscles  are  seated  have  no 
blood-vessels. 

The  veins  are  arranged  on  the  same  plan  as  the  arteries  : 
they  form  a  superficial  and  a  deep  layer,  and  have  their  origin 
in  the  papillae.  From  the  superficial  layer  larger  vessels  pass 
downward,  receiving  blood  from  the  veins  of  the  hair-follicles, 
sebaceous  glands,  and  the  general  tissue  of  the  corium,  thus 
forming  a  deep  subcutaneous  layer  or  venous  network. 

Nerves. — Medullated  and  non-medullated  nerve-fibres  are 
present  in  the  skin.  They  are  found  in  combination  in  the  nerve- 
trunks  of  the  subcutaneous  tissue,  the  medullated  fibres  being 
most  numerous  in  those  regions  of  the  skin  where  the  Pacinian 
and  tactile  corpuscles  are  most  abundant.  In  the  subcuta- 
neous connective-tissue  region,  and  in  the  lower  part  of  the 
corium,  some  nerve-fibres  leave  the  nerve-trunks  and  pass  to 
the  glands,  blood-vessels,  and  Pacinian  corpuscles  found  in  this 
region.  In  the  corium  some  of  the  fibres  lose  their  medullary 


280  MANUAL    OF    HISTOLOGY. 

sheath,  and  afterward  continue  their  course  as  non-medullated 
fibres.  The  nerve-bundles  pass  upward  in  a  more  or  less  oblique 
direction  from  the  subcutaneous  connective  tissue  through  the 
corium  to  the  subpapillary  network  of  blood-vessels,  around 
which  they  form  a  plexus.  From  this  subpapillary  plexus 
medullated  fibres  run  upward  and  pass  into  the  tactile  cor- 
puscles. 

The  non-medullated  nerve-fibres  form  a  reticulum  around 
the  blood-vessels  of  the  pars  reticularis  corii  and  the  capilla- 
ries of  the  papillae.  They  consist  of  thick  or  fine,  smooth, 
varicose  fibres  with  numerous  nuclei.  These  fibres  proceed 
from  the  network  around  the  subpapillary  blood-vessels  up- 
ward toward  the  rete  Malpighii,  and  either  pass  directly  into 
the  rete  or  run  for  a  short  distance  parallel  to  its  under  sur- 
i'ace,  and  then  finally  enter  that  layer.  Within  the  epider- 
mis the  fibres  run  between  the  cells  and  terminate  in  a  manner 
not  yet  definitely  known.  Their  mode  of  division  and  termina- 
tion within  the  epidermis  is  probably  similar  to  that  occurring 
in  the  cornea.  Within  the  papillae  the  nerve-fibres  frequently 
divide  before  entering  the  rete. 

The  manner  of  distribution  and  termination  of  the  non- 
medullated  nerve-fibres  can  only  be  studied  successfully  in  tis- 
sue stained  with  gold  chloride.  The  tissue  must  be  fresh,  and 
a  weak  solution  of  the  gold  chloride  used.  When  sufficiently 
stained  the  tissue  is  placed  in -distilled  water  slightly  acidu- 
lated with  acetic  acid  and  exposed  to  the  light. 

The  Pacinian  corpuscles  are  found  in  greatest  abundance  in 
the  skin  of  the  fingers,  toes,  palm  of  the  hand,  sole  of  the  foot, 
but  also  occasionally  in  other  regions  of  the  skin.  Their  struc- 
ture is  described  in  the  article  on  the  nervous  system. 

Tactile  corpuscles.— As  already  mentioned,  some  of  the 
medullated  nerve-fibres  forming  the  plexus  surrounding  the 
subpapillary  blood-vessels,  pass  upward  and  enter  the  so-called 
tactile  corpuscles.  These  corpuscles  are  generally  seated  in  the 
papillae,  but  occasionally  they  are  found  in  the  subpapillary 
region,  i.e.,  the  upper  part  of  the  corium.  The  majority  of 
the  papillae  containing  such  corpuscles  have  no  blood-vessels. 
They  are  more  or  less  oval  in  form,  and  can  be  easily  recog- 
nized under  the  microscope  by  their  dark  contours  and  by  the 
oblique  lines  produced  by  the  transversely  running  connective- 
tissue  fibres  of  the  outer  surface  of  the  corpuscle.  There  may 


THE    SKIN. 


281 


be  two  or  more  corpuscles  within  a  single  papilla  (Thin),  but 
each  corpuscle  invariably  has  a  special  nerve  passing  into  it. 
Frequently,  however,  an  appearance  as  if  two  corpuscles  were 
present  is  produced  by  a  single  corpuscle  having  the  shape 
of  a  figure  8.  The  medullated  nerve-fibre,  in  passing  to  the 
corpuscle,  pursues  a  more  or  less  curved  course,  and  usually 
enters  it  at  or  near  its  lower  extremity.  It  may,  however,  en- 
ter at  any  part  of  the  corpuscle,  and  sometimes  winds  around 
it  for  a  considerable  distance  before  entering.  After  entering 
the  corpuscle  the  medullary  sheath  is  lost,  and  its  course  now 
becomes  difficult  to  pursue,  except  in  the  case  of  very  small 
or  young  corpuscles.  The  intimate  structure  of  these  bodies 
and  the  arrangement  of  their  formative  elements  are  still  mat- 
ters of  discussion  and  uncertainty.  The  external  portion  of  a 
corpuscle  appears  to  be  composed,  in  great  part,  of  larger  or 
smaller  bundles  of  white,  fibrous  connective  tissue  anastomos- 
ing with  each  other  and  running  transversely,  or  in  a  spiral 
direction,  to  the  long  diameter  of  the  corpuscle.  This  part 
of  the  corpuscle  differs,  as  regards 
irregularity  of  surface,  with  the  size 
and  the  manner  in  which  the  fibrous 
fascicles  divide  and  anastomose.  The 
coarser  the  bundles  and  the  anastomo- 
ses the  more  irregular  will  be  its  sur- 
face. Between  the  fibres  are  found 
oval  or  round  bodies  which  color  deep- 
ly in  gold,  and  have  been  regarded  as 
elastic  elements  (Thin).  Other  obser- 
vers consider  them  as  connective  tis- 
sue, or  nerve-fibres.  Some  of  these 
bodies  undoubtedly  represent  the 
nerve-fibre  in  transverse  or  oblique 
section  ;  for  the  nerve  pursues  a  more 
or  less  zigzag  course  within  the  corpuscle,  and,  consequently, 
a  section  of  the  body  will  probably  show  the  nerve  cut  across 
in  one  or  more  places  (Pig.  120,  b).  The  arrangement  of  the 
elements  forming  the  central  part  of  the  corpuscle  is  not  yet 
thoroughly  understood.  These  bodies  have  hitherto  been 
usually  regarded  as  end-organs — that  is,  it  has  been  believed 
that  the  medullated  nerve-fibre  terminates  within  the  corpuscle, 
hence  the  name,  tactile  corpuscle.  Observers,  however,  have 


Fio.  120. — Tactile  corpuscle,  show- 
ing termination  of  nerve :  a,  corpuscle; 
6,  nerve,  cut  obliquely;  c,  apparent 
division  of  nerve-fibre ;  e,  similar  ap- 
pearance as  at  c ;  /,  blood-vessel ;  g, 
rete  cells;  A,  nerve-fibre  cut  trans- 
versely. 


282  MANUAL    OF    HISTOLOGY. 

not  agreed  as  to  the  mode  of  termination  of  the  nerve,  and 
some  have  maintained  that  it  has  not  been  clearly  proven  that 
they  really  do  terminate  in  the  corpuscle.  From  specimens 
which  I  have  recently  obtained  I  am  led  to  believe  that  the 
nerve  does  not  terminate  within  the  corpuscle,  but  passes  on 
into  the  rete  Malpighii. 

The  best  corpuscles  for  studying  this  point  are  small  ones, 
as  in  these  a  section  is  more  likely  to  include  the  entire  upper 
extremity  of  the  corpuscle  at  the  same  time  that  it  is  not  too 
thick  for  examination  with  the  microscope.  Even  in  a  small 
corpuscle,  however,  unless  the  nerve  passes  onward  in  a  direct 
level  with  the  corpuscle  after  leaving  it,  the  nerve,  in  a  vertical 
section,  will  be  cut  across,  and  it  will,  therefore,  be  impossible 
to  follow  it  from  the  corpuscle  into  the  rete.  I  believe  the 
nerve  frequently,  perhaps  generally,  changes  the  direction  of 
its  course  after  leaving  the  corpuscle,  and  hence  we  often  see 
a  transverse  section  of  the  nerve  at  the  upper  extremity  of  the 
corpuscle.  In  Fig.  120  is  seen  the  location  of  the  termination 
of  the  nerve-fibre  as  observed  in  one  of  my  specimens.  In 
one  place  its  course  between  the  rete  cells  was  very  indistinct, 
though  recognizable.  The  nerve  passed  obliquely  upward  be- 
tween the  cells  of  the  rete  to  the  space  between  the  second 
and  third  rows  of  cells,  where  it  assumed  a  longitudinal  di- 
rection. At  the  commencement  of  the  curve  the  nerve  ap- 
peared to  have  undergone  division  (c).  After  passing  a  short 
distance  horizontally  it  ran  almost  perpendicularly  downward, 
and  near  g  was  lost  to  view.  At  e  it  appeared  to  have  again 
undergone  division.  According  to  the  appearances  here  fig- 
ured the  corpuscles  are  not  the  structures  in  which  the  nerve 
terminates,  the  latter  passing  from  the  corpuscle  (as -a  non- 
medullated  fibre)  into  the  epidermis,  where  it  divides  and 
probably  terminates  in  the  same  manner  as  the  other  nerves. 
This  mode  of  termination  cannot  be  regarded  as  strange,  as  we 
have  already  seen  that  some  medullated  nerve-fibres  lose  their 
medulla  deeper  in  the  corium,  and  afterward  continue  their 
course  as  non-medullated  fibres. 

The  tactile  corpuscles  are  found  in  greatest  number  in 
the  ends  of  the  fingers.  They  are  also  present  on  other  parts 
of  the  hand  and  on  the  foot,  and  sometimes  in  the  lips  and 
nipple. 

The  sweat-glands.—  The  sweat-glands— glandulce  sudorif- 


THE 


283 


erce — are  found  in  the  skin  of  all  parts  of  the  body  except  that 
of  the  glans  penis  and  margin  of  the  lips.  They  are  most  nu- 
merous in  the  palms  of  the  hands  and  the  soles  of  the  feet, 
where  they  number,  according  to  Krause,  2,685  to  2,736  to  the 
square  inch. 

A  sweat-gland  is  composed  of  two  parts,  viz.:  the  gland 
proper,  or  secreting  part,  and  an  excretory  duct.  The  gland 
proper  lies  in  the  subcutaneous  tissue, 
and  consists  of  the  lower  part  of  the  sweat- 
gland  rolled  and  coiled  upon  itself  into  a 
more  or  less  globular  form,  the  tube  ter- 
minating in  a  cul-de-sac,  the  blind  extrem- 
ity generally  lying  in  the  centre  of  the  coil. 
The  diameter  of  the  secreting  tube  is 
greater  than  that  of  the  excretory  duct. 
The  former  is  composed  of  secreting  cells, 
unstriped  muscular  fibres,  and  a  basement- 
membrane.  The  cells  (glandular  or  secret- 
ing epithelial  cells)  are  polygonal  in  shape 
and  form  only  a  single  layer.  They  are 
strongly  granular  in  appearance  and  have 
a  very  distinct  nucleus.  Their  basal  end 
is  sometimes  notched  where  they  are  in- 
serted into  the  basement-membrane.  In 
normal  conditions  these  bodies  are  never 
found  in  the  sweat-fluid,  but  in  inflamma- 
tion of  the  surrounding  connective  tissue 
they  frequently  become  separated  from 
the  basement-membrane.  Oil-globules  are  frequently  seen  in 
the  cell- body,  and  are  to  be  regarded  as  a  normal  constituent 
of  the  corpuscles. 

The  basement-membrane  is  a  thin,  transparent  structure, 
lying  beneath  the  epithelial  cells  and  composed  of  flat  endo- 
thelial  elements,  as  shown  by  the  action  of  silver  nitrate  on 
the  fresh  tissue. 

In  certain  glands,  especially  those  of  the  axilla,  a  layer  of 
unstriped  muscular  fibres  is  found  external  to  the  basement- 
membrane.  These  fibres  are  present  in  only  a  small  number 
of  sweat-glands ;  by  their  contraction  they  assist  in  the  expul- 
sion of  the  secreted  sweat.  They  are  the  smallest  unstriped 
muscular  fibres  met  with  in  the  human  body. 


FIG.  121. — Lower  part  of  a 
sweat-gland :  a,  excretory  duct ; 
6,  coil  of  secreting-tube ;  c,  sc- 
creting-tube  cut  transversely; 
d  blood-vessels  cut  across. 


284  MANUAL    OF   HISTOLOGY. 

The  sweat-glands  are  surrounded  by  a  somewhat  loose 
fibrous  connective  tissue,  from,  which  fibres  pass  inward  and 
form  a  closer  network  between  the  coils  of  the  gland.  Some 
of  the  fibres  run  parallel,  and  others  transversely  or  obliquely, 
to  the  long  diameter  of  the  convoluted  tube.  A  large  number 
of  lymphoid  cells  are  always  present  in  this  interglandular 
connective  tissue.  The  sweat-glands  are  richly  supplied  with 
blood-vessels. 

The  excretory  duct  passes  upward  from  the  gland  proper 
in  a  more  or  less  vertical  direction  through  the  different  layers 
of  the  skin  to  its  free  surface,  where  it  opens  with  a  funnel- 
shaped  orifice.  In  passing  through  the  corium  it  pursues  a 
straight  or  slightly  wavy  course,  and  enters  the  lowest  part 
of  the  inter-papillary  rete.  The  structure  of  this  part  of 
the  excretory  duct  differs  from  that  of  the  gland  proper,  in 
the  shape  of  the  cells,  the  absence  of  muscle-fibres,  and  the 
presence  of  a  cuticula.  This  cuticula  lines  the  inner  surface 
of  the  epithelial  coating  and  limits  the  lumen  of  the  duct. 
As  the  rete  Malpighii  is  entered  there  are  generally  two  or 
more  layers  of  cells  lining  the  duct,  the  number  increasing 
as  the  rete  is  approached.  The  transition  from  secreting  cells 
to  lining  cells  is  gradual,  so  that  the  presence  of  a  cuticula 
decides  the  nature  of  the  tube.  The  basement -membrane 
corresponds  in  structure  with  that  of  the  gland  proper.  The 
fibres  of  surrounding  connective  tissue  run  parallel  with  the 
duct. 

As  the  duct  approaches  the  rete  Malpighii  its  epithelial 
cells  increase  in  number  and  form  two  or  more  layers,  which 
are  really  only  a  continuation  downward  of  the  cells  of  the 
rete.  When  the  duct  enters  the  rete  it  loses  its  basement- 
membrane  and  is  formed  only  of  the  cells  of  the  mucous  layer, 
which  have  become  more  or  less  flattened  and  spindle-shaped. 
The  direction  of  the  duct  through  the  rete  is  sometimes  straight 
and  sometimes  spiral. 

In  passing  through  the  stratum  corneum  the  duct  pursues 
a  spiral  direction  on  account  of  the  horizontally  flattened  cells 
of  this  layer  (see  Fig.  114,  /),  and  the  number  of  spirals  pres- 
ent depends  upon  its  thickness.  The  largest  number  is  found 
in  the  palms  of  the  hands  and  soles  of  the  feet,  where  it  may 
amount  to  twenty  or  more,  whilst  on  some  parts  of  the  body 
there  is  not  even  a  single  complete  spiral.  The  wall  of  the 


THE    SKIN.  285 

duct  is  formed  of  the  cells  of  tlie  corneous  layer,  and  the  duct 
opens  on  the  free  surface  at  the  summit  of  the  ridges. 

The  formation  of  the  sweat-glands  commences  in  the  fifth 
month  of  foetal  life  by  the  pushing  of  epithelial  cells  from  the 
rete  mucosum  into  the  cutis.  In  the  seventh  month  the  epi- 
thelial cells  form  a  canal,  and  the  lower  end  of  the  tube  be- 
comes dilated  and  somewhat  twisted.  In  the  ninth  month  the 
tube  is  coiled  upon  itself  to  form  the  gland  proper.  According 
to  Ranvier,  who  believes  that  the  muscular  fibres  lie  between 
the  epithelial  cells  and  the  basement-membrane,  the  muscle- 
cells  arise  from  the  external  cells  of  the  gland  proper  by  a 
process  of  simple  differentiation.  The  lumen  of  the  tube  is 
formed  not  by  a  softening  down  of  the  central  cells,  but  by  the 
formation  of  the  cuticula,  which  occurs  first  at  the  lowest  part 
of  the  excretory  duct  (Ranvier). 

The  sebaceous  glands. — The  sebaceous  glands  are  seated  in 
the  corium  and  are  in  close  connection  with  the  hair-follicles. 
When  the  hairs  are  large  the  sebaceous  glands  appear  as  ap- 
pendages to  the  hair-follicles  into  which  their  ducts  enter,  and 
by  which  their  contents  are  carried  to  the  free  surface.  As 
regards  the  small  downy,  or  lanugo  hairs,  they  may  be  said  to 
open  into  the  ducts  of  the  sebaceous  glands,  the  ducts  of  the 
latter  having  in  this  case  a  much  greater  diameter  than  in  the 
previous  instance.  They  also  open  directly  on  the  free  surface. 

The  sebaceous  glands  are  almost  without  exception  acinous 
glands,  the  number  of  lobules  forming  a  single  gland,  ranging 
from  two  to  twenty,  or  more.  The  largest  glands  are  seated  in 
the  nose,  cheeks,  scrotum,  about  the  anus,  and  in  the  labia. 
Occasionally  the  secreting  portion  of  a  sebaceous  gland  con- 
sists of  a  single  tubule,  or  sac,  whose  duct  opens  into  a  hair- 
follicle. 

Every  sebaceous  gland  is  composed  of  two  parts,  viz.:  the 
secreting  portion,  or  gland  proper,  and  the  duct.  The  gland 
proper  is  formed  of  a  basement-membrane,  or  sac,  externally, 
and  secreting  cells,  or  their  products,  internally.  The  basement- 
membrane  is  continuous  with  the  transparent  membrane  de- 
scribed as  lying  directly  beneath  the  rete  Malpighii  and  above 
the  corium,  and  has  a  similar  structure.  This  basement-mem- 
brane passes  from  the  sebaceous  gland  to  the  hair-follicle,  where 
it  forms  the  inner  layer  of  the  hair-sac.  The  membrane  of  the 
sebaceous  gland  is  surrounded  externally  by  bands  of  dense 


286  MANUAL    OF    HISTOLOGY. 

connective  tissue  containing  blood-vessels,  nerves,   and  lym- 
phatics. 

The  secreting  part  of  the  gland  (Fig.  122,  t)  is  composed  of 
layers  of  cells  very  similar  to  the  cells  present  in  the  epidermis, 
those  of  the  outer  part  corresponding  to  the  cells  of  the  rete 
Malpighii.  The  first  layer  of  cells,  viz.,  those  seated  upon  the 
basement-membrane,  is  composed  of  cylindrical,  or  cubical, 
cells,  like  those  of  the  rete.  They  have  a  very  distinct  nucleus. 
Further  inward  the  cells  become  larger,  more  or  less  polyhe- 
dral in  form,  and  contain  fat,  which  obscures  or  conceals  the 
nucleus.  If  the  fat  is  extracted  the  nucleus  can  be  seen  lying 
in  the  centre  of  the  space  previously  occupied  by  the  fat.  The 
nearer  the  centre  of  the  gland  the  greater  the  quantity  of  fat 
in  the  cells.  The  most  external  layer  of  cells  contains  but  a 
small  quantity.  In  the  centre  of  the  gland,  free  fat,  fat-crys- 
tals, and  remnants  of  epithelial  cells  are  found. 

The  duct  of  the  sebaceous  gland  is  similar  in  structure  to 
that  of  the  gland  proper.  Externally  is  the  basement-mem- 
brane, lined  inside  by  epidermis-like  cells,  containing  more  or 
less  fat,  and  enclosing  a  central  cavity  through  which  the  seba- 
ceous matter  passes  to  reach  the  hair-follicle  or  the  free  surface. 
The  contents  of  this  canal  are  fat,  fat-crystals,  and  remnants 
of  epithelial  cells.  Internal  to  the  polyhedral  cells  of  the  duct 
are  the  cells  of  the  corneous  layer  of  the  epidermis,  which  di- 
minish in  number  in  proportion  to  the  distance  from  the  free 
surface. 

In  large  hairs  the  duct  of  the  sebaceous  gland  opens  at  an 
acute  angle  into  the  hair-follicle  near  its  upper  third,  and  the 
gland  proper  lies  about  on  a  level  with  the  middle  third  of  the 
hair-follicle. 

At  the  place  of  union  of  the  hair-follicle  with  the  sebaceous 
gland  the  cells  of  the  latter  become  continuous  with  the  cells 
of  the  external  root-sheath  of  the  hair.  This  latter  root-sheath 
becomes  continuous  above  with  the  cells  of  the  rete  Malpighii. 

The  development  of  the  sebaceous  glands  commences  at  the 
third  month  of  foetal  life,  as  a  projection  downward  and  out- 
ward of  a  part  of  the  external  root-sheath  of  the  hair,  at  the 
place  where  the  future  opening  of  the  duct  will  be  situated. 
It  consists,  at  first,  entirely  of  epithelial  cells,  which  by  sub- 
sequent multiplication  and  further  projection  downward,  form 
the  sebaceous  gland. 


THE    SKIN.  287 

Muscles. — Striated  and  non-striated  muscles  are  present  in 
the  skin.  The  former  are  found  both  in  the  smooth  and  in  the 
bearded  parts  of  the  face,  and  also  in  the  nose.  They  arise  from 
the  deeply  seated  muscles,  and  passing  vertically,  or  more  or 
less  obliquely,  upward  between  the  hair-follicles  and  the  glands 
of  the  skin,  terminate  in  the  corium. 

The  non-striated  muscles  are  very  numerous,  and  run  either 
in  a  parallel  or  in  an  oblique  direction  to  the  general  surface 
of  the  skin.  Those  lying  parallel  with  the  general  surface  run 
either  in  a  straight  or  circular  direction.  When  they  run  in  a 
straight  direction  and  anastomose  with  each  other  they  form 
a  network,  as  in  the  scrotum,  prepuce,  and  perineum.  The 
straight  running  muscles  are  found,  especially  in  the  scalp  and 
in  the  axilla,  both  above  and  below  the  sweat-glands.  Where 
the  muscles  have  a  circular  course,  as  in  the  areola  of  the  nip- 
ple, a  continuous  ring  muscle  is  formed. 

The  majority  of  the  muscles  running  in  an  oblique  direc- 
tion have  a  special  relation  to  the  hair-follicles.  The  muscle 
arises  from  the  internal  sheath  of  the  hair-follicle  and  passing 
obliquely  upward,  skirting  the  lower  surface  of  the  sebaceous 
gland,  terminates  in  the  upper  part  of  the  corium  (Fig.  122,  ri). 
Occasionally  two  muscles,  situated  on  opposite  sides,  arise 
from  a  single  hair-follicle  sheath.  A  muscle  in  its  course  up- 
ward frequently  divides  into  two  or  more  bundles,  these  sec- 
ondary bundles  afterward  pursuing  different  directions  from 
each  other,  and  sometimes  uniting  with  fibres  from  other  mus- 
cles, form  a  network  in  the  corium.  Sometimes  an  entire 
muscle,  or  a  secondary  bundle,  passes  upward  into  a  papilla 
of  the  cutis  and  is  inserted  into  the  dense  fibrous  connective  tis- 
sue directly  beneath  the  rete  Malpighii.  Occasionally  several 
secondary  bundles  run  nearly  parallel  with  each  other  and  ter- 
minate either  separately  in  the  corium,  or  conjointly,  after 
uniting. 

The  skin  is  provided  with  other  muscles  which  have  no  spe- 
cial relation  to  the  hair- follicles,  but  pass  more  or  less  verti- 
cally upward  from  the  subcutaneous  tissue  to  be  inserted  in 
the  corium. 

The  number  of  muscles  present  in  the  skin  varies  in  differ- 
ent regions  of  the  body.  They  are  most  numerous  in  the  scro- 
tum. The  order  of  frequency  in  the  different  parts  of  the  body 
is  as  follows  :  Scrotum,  penis,  anterior  part  of  perinseum,  scalp, 


288 


MANUAL    OF   HISTOLOGY. 


forearm,  thigh,  arm,  shoulder,  forehead,  abdominal  wall,  ax- 
illa, fore-leg,  face,  volar  and  dorsal  surfaces  of  the  hands  and 

feet  (Neumann).  They  are  less 
developed  on  the  flexor  than  on 
the  extensor  surfaces. 

The  size  of  the  individual  mus- 
cles varies  according  to  the  person 
and  the  region  of  the  body.     It  is 
impossible,  therefore,  to  recognize 
with  certainty  a  slight  hypertro- 
phy or  atrophy  of  these  structures. 
For  information  as    to    their 
blood,  lymph,  and  nerve  supply 
see  the  article  on  unstriped  muscle. 
TJie   Jiair. — The  parts  to  be 
studied  in  connection  with  the  hair 
proper  are  the  hair-follicle  and 
the  hair-papilla.    Tb e  hair  proper 
is  a  cylindrical  structure  seated 
within  the  hair-follicle  and  upon 
the  hair-papilla.      Its    base  lies 
embedded  either  in  the  subcuta- 
neous connective  tissue  or  in  the 
corium.     The  portion  of  the  hair 
proper  within  the  follicle  is  called 
the  root  of  the  hair,   and  the  re- 
mainder the  shaft  of  the  hair. 
The  true  hair-follicle  includes  all 
that  part  of  the  hair-sac  below 
the  place  where   the    sebaceous 
duct  enters  the  hair- follicle.     It 
is  of  very  variable  size  and  con- 
sists of  a  blind  extremity  and  a 
funnel  -  shaped  orifice  (a).     The 
follicle  is  narrowed    just    below 
this    funnel-shaped    orifice    and 
forms  the  so-called   neck  of  the 
hair-follicle  (5).     This  is  the  nar- 
rowest part  of  the   follicle,   and 
is  the  place  where  the  duct  of  the  sebaceous  gland  enters. 
From  the  neck  downward  the  hair-follicle  increases  in  size,  be- 


Fio.  122.— Hair  from  beard :  a,  canal  of 
exit ;  ft,  neck  of  hair-follicle ;  c,  lower  part  of 
hair-follicle :  d,  external  sheath  of  hair-folli- 
cle ;  e,  internal  sheath  of  hair-follicle :  /,  ex- 
ternal root-sheath  of  hair;  gr,  internal  root- 
Bheath  of  hair ;  h,  cortical  substance ;  k,  me- 
dulla of  hair;  /,  root  of  hair  ;  m,  fat-cells ;  n, 
arector  pili ;  o,  papillae  of  skin  ;  p,  papilla  of 
hair ;  «,  rete  mucosum ;  t,  sebaceous  gland  ; 
ep,  stratum  corneum,  which  is  continued  into 
the  follicle.  Biesiadecki. 


THE    SKIN.  289 

ing  largest  at  its  lower  end,  where  it  rests  upon  the  papilla. 
Below  the  neck  we  have  the  follicle  and  the  root  of  the  hair. 

The  follicle  consists,  anatomically,  of  three  layers :  the  ex- 
ternal, middle,  and  internal  hair-follicle  sheaths. 

The  external  sheath  of  the  follicle  (d)  consists  of  connective- 
tissue  fibres,  which  extend  from  the  upper  corium  and  running 
parallel  to  the  long  axis  of  the  hair-follicle  surround  the  base 
of  the  latter  and  send  some  fibres  into  the  papilla.  The  fibres 
forming  the  inner  portion  of  this  sheath  are  arranged  much 
more  closely  than  the  fibres  forming  the  external  part.  In  this 
latter  situation  there  is  no  sharp  dividing  line  between  the 
sheath  and  the  surrounding  loose  connective  tissue,  the  one 
merging  gradually  into  the  other.  Within  this  sheath  run  the 
special  blood-vessels  and  nerves  of  the  hair-follicle. 

The  middle  sheath  of  the  follicle  consists  of  a  few  transverse- 
ly running  connective-tissue  fibres,  between  which  lie  oval  nuclei 
imbedded  in  a  granular  substance.  Tliese  latter,  probably, 
represent  organic  muscle-cells.  This  sheath  begins  at  the  neck 
of  the  follicle  and,  surrounding  its  lower  part,  passes  also  within 
the  papilla.  In  this  tissue  is  a  close  network  of  blood-capil- 
laries. Nerves  have  not  as  yet  been  observed,  though  they 
probably  exist. 

The  internal  sheath  of  the  follicle  is  composed  of  a  trans- 
parent, homogeneous-looking  structure — the  basement-mem- 
brane, which  is  riot  altered  by  the  action  of  acids  or  alkalies. 
It  is  merely  a  continuation  of  the  transparent  membrane  found 
between  the  rete  mucosurn  and  the  corium,  which  it  resembles 
in  its  structure.  It  contains  neither  blood-vessels  nor  nerves. 
The  external  surface  is  smooth,  but  the  internal  surface  has  a 
notched  appearance,  caused  by  prolongations  inward  between 
the  cells  of  the  external  root-sheath  of  the  hair. 

The  hair -papilla  is  formed  from  the  stroma  of  the  hair-fol- 
licle sheaths,  especially  from  that  of  the  middle  sheath.  It 
consists  of  connective-tissue  fibres,  between  which  are  found 
numerous  round  cells.  The  internal  follicle  sheath  separates 
it  from  the  root  of  the  hair.  Within  the  papilla  are  found 
one  or  more  arteries  and  veins  besides  non-medullated  nerve- 
fibres.  The  papilla  has  a  narrow  neck,  a  thicker  body,  and 
a  conical  apex.  It  is,  on  an  average,  twice  as  long  as  it  is 
broad.  The  breadth  is  in  direct  proportion  to  the  length  of 
the  hair. 


290  MANUAL    OF    HISTOLOGY. 

The  hair-follicles  and  hairs  stand  obliquely  to  the  surface 
of  the  skin.  Their  direction  varies  in  different  regions  of  the 
body,  and  depends  upon  the  structure  of  the  connective  tissue 
of  the  corium  and  the  degree  of  its  tension.  The  contents  of 
the  hair-follicles  are  the  external  and  internal  root-sheaths  and 
the  hair  proper. 

The  external  root-sheath  (/)  adjoins  the  inner  follicle  sheath 
and  consists  of  rete  cells  continued  into  the  hair-follicle  from 
the  general  rete  mucosum  layer  of  the  skin.  This  sheath  does 
not  extend  as  far  as  the  lowest  part  of  the  follicle,  generally 
ending  about  on  a  level  with  the  apex  of  the  hair-papilla, 
though  it  is  sometimes  continued  as  far  as  the  base  of  the 
latter.  All  the  different  kinds  of  cells  present  in  the  epi- 
dermis are  also  found  in  this  sheath  as  far  down  as  the  neck 
of  the  follicle.  Beyond  this  point  the  cells  of  the  rete  Mal- 
pighii  only  enter  into  its  formation.  The  number  of  rows  of 
cells  forming  it  is  subject  to  great  variation.  It  diminishes 
as  the  base  of  the  follicle  is  approached,  so  that  finally  the 
sheath  is  formed  of  a  single  row  of  cells.  At  the  neck  of 
the  follicle  the  sheath  is  usually  narrower  than  directly  above 
or  below  this  point,  owing  to  the  pressure  to  which  the  cells 
are  here  subjected.  Their  form  is  very  similar  to  that  of 
the  corresponding  cells  of  the  rete  mucosum.  Those  of  the 
deepest  row  are  cylindrical,  and  those  of  the  second  row 
polyhedral.  In  the  other  rows  the  cells  are  flatter,  with  the 
exception  of  the  most  internal  row,  where  all  these  bodies 
are  large  and  round.  This  last  row  is  not  subject  to  the  same 
changes  as  the  others,  and  has  been  considered  to  be  a  distinct, 
independent  row  of  cells  (Unna).  The  nuclei  of  all  the  cells 
color  strongly  in  carmine,  haematoxylon,  etc.  Nerve-fibres  have 
been  described  as  running  between  the  cells  of  this  sheath 
(Langerhans). 

The  internal  root-sheath  (g)  lies  in  direct  contact  with  the 
external  root-sheath.  It  is  usually  described  as  consisting  of 
two  layers,  an  external  one,  also  called  the  sheatli  of  Henle, 
and  an  internal  one,  or  slieath  of  Huxley.  Strictly  speak- 
ing, this  division  into  two  sheaths  is  incorrect,  as  it  has  been 
shown  (Unna)  that  the  two  sheaths  supposed  to  be  distinct 
have  a  common  origin  from  the  cylindrical  epithelial  cells  sur- 
'rounding  the  neck  of  the  hair-papilla  at  its  lowest  part.  These 
cells  color  very  deeply  in  carmine.  They  surround  the  root  of 


THE    SKIN.  291 

the  hair  like  a  sheath.  In  the  thick  hairs  of  the  beard  the 
sheath  consists  of  three  rows  of  cells — the  external  row,  after- 
ward forming  Henle's  sheath,  and  the  two  inner  rows  of  cells, 
the  sheath  of  Huxley.  In  finer  hairs  there  are  only  two  layers  of 
such  cells.  These  corpuscles  are  originally  similar  in  structure, 
having  a  very  granular  appearance  and  an  indistinct  nucleus. 
The  sheath  is  thinnest  where  the  hair-papilla  is  broadest. 
The  cells  of  the  external  layer  (Henle's)  become  paler  and  lose 
their  nuclei  earlier  than  those  of  the  inner  layer,  so  that  on  a 
level  with  the  upper  part  of  the  papilla  there  is  a  marked  dif- 
ference in  the  appearance  of  the  two  layers  of  cells.  Formerly 
it  was  supposed  (Biesiadecki)  that  Henle's  sheath  commenced 
at  this  point  and  was  a  product  of  the  external  root-sheath, 
corresponding  in  this  respect  with  the  corneous  layer  of  the 
epidermis.  The  cells  of  Huxley's  layer  afterward  become 
transparent  also  and  lose  their  nuclei,  and  can  then  no  longer 
be  distinguished  from  the  cells  of  Henle's  layer.  The  internal 
root-sheath  is  now  formed  of  transparent,  non-nucleated,  spin- 
dle-shaped, or  flattened  bodies  which  surround  the  hair-cutl- 
cula  as  far  as  the  neck  of  the  hair- follicle. 

Within  the  internal  root-sheath  lies  the  liair  proper,  which 
consists  of  a  knobbed  extremity,  the  root  of  the  hair,  and  a 
cylindrical  portion,  the  shaft.  Between  the  hair  proper  and 
Huxley's  layer  lies  the  hair-cuticula.  This  latter  consists  of 
two  rows  of  cells — an  external  one,  closely  united  with  Hux- 
ley's layer,  and  an  internal  one,  united  to  the  hair-shaft.  They 
both  arise  from  the  cylindrical  cells  seated  directly  upon  the 
upper  part  of  the  neck  of  the  papilla  to  the  inside  of  the  cells 
producing  the  internal  root-sheath.  The  cells  of  the  inner 
cuticula  (the  hair-cuticula)  are  at  first  round,  then  cuboid  in 
form,  and  finally,  long  and  prismatic.  Above  the  papilla  they 
are  more  elongated,  and  commence  to  overlap  the  cells  above 
them,  With  the  flattening  out  of  the  cells  they  assume  the 
form  of  rhomboid  or  ovoid  plates,  so  that  above  the  free  sur- 
face of  the  skin  one  cell  partly  covers  the  bodies  of  four  or  five 
others.  At  first  they  lie  perpendicularly  to  the  long  axis  of  the 
hair,  but  afterward  they  are  parallel  with  it.  Above  the  papilla 
they  form  spiral  rows  around  the  hair  shaft,  so  that  in  any  sec- 
tion of  this  part  the  cells  appear  of  a  long  cylindrical  or  spin- 
dle-shape. The  external  or  root-sheath  cuticula  consists  at 
first  of  round  cells  which  afterward  flatten  and  lie  in  the  same 


292 


MANUAL    OF    HISTOLOGY. 


direction  as  the  flat  cells  of  the  previous  cuticula.  Before  the 
internal  root-sheath  is  pierced  by  the  growing  hair  both  cuti- 
culse  are  composed  of  similar  cells. 

The  root  of  the  hair  consists  of  cells  closely  resembling 
those  of  the  rete  mucosum.  The  corpuscles  seated  directly 
upon  the  basement-membrane  of  the  papilla  are  cylindrical  in 
form,  and  the  more  superficial  ones  polyhedral.  Near  the  hair- 
shaft  they  are  spindle-shaped  and  firmer.  The  lower  cells  of 
the  central  part  of  the  root  of  the  hair  are  round,  have  a  large 
nucleus,  and  a  small  amount  of  cell-body.  Afterward  the  cell- 
body  increases  in  size.  They  bear  a  close  resemblance  to  em- 
bryonic corpuscles  and  color  deeply  in  carmine.  In  the  upper 
part  of  the  root  of  the  hair  the  cells  of  the  external  part  of  the 
bulb  become  oblong,  spindle-formed,  and,  finally,  are  lengthened 

out  like  fibres,  in  which  condition  they 
form  the  fibrous  part  of  the  hair-shaft. 
The  pigment  in  the  root  of  the  hair  is 
sharply  limited  externally  by  the  cells 
of  the  hair-cuticula. 

The  shaft  of  the  hair  consists  of  a 
central  part  or  medulla,  and  a  fibrous 
portion  covered  by  the  hair-cuticula. 
The  medulla  consists  of  polyhedral 
cells  containing  fat  and  pigment  gran- 
ules. Toward  the  free  end  of  the  hair 
it  becomes  smaller,  and  finally  ends 
near  the  point.  The  fibrous  portion 
forms  the  principal  part  of  the  hair- 
shaft,  and  consists  of  flattened,  fusi- 
form cells,  containing  numerous  spin- 
dle-shaped granules. 

From  the  foregoing  description  of 
the  hair  and  its  follicle  it  is  clear  that 
in  transverse  sections  it  will  present 
different  appearances,  according  to  the 

situation  in  which  the  section  is  made.  A  description  of  trans- 
verse sections  in  different  regions  of  the  hair  is  here  unneces- 
sary. We  reproduce,  however,  above,  a  figure  from  Biesiadecki, 
which  will  sufficiently  explain  this  matter  (Fig.  123). 

A  hair  increases  in  length  by  the  formation  of  new  elements 
in  its  root,  and  they,  by  their  subsequent  elongation  and  move- 


Pio.  123.— Transverse  section  of 
the  hair  beneath  the  neck  of  the  hair- 
follicle  :  a.  external  sheath  of  the  hair- 
follicle  ;  fe,  transversely  cut  blood-ves- 
sels ;  c,  inner  sheath  of  hair-follicle ; 
d,  basement-membrane  of  hair-follicle; 
«,  extern^  root-sheath  ;/,  cells  of  Hen- 
le's  layer;  g,  cells  of  Huxley's  layer; 
A,  cuticula  ;  J,  hair-shaft. 


THE    SKIN.  2S3 

ment  upward,  push  the  shaft  of  the  hair  and  its  cuticula  before 
them.  The  structure  of  an  adult  hair  can  be  best  studied  iu 
the  stiff,  gray  hairs  of  the  beard.  For  the  study  of  the  origin 
of  the  root-sheaths  young  hairs  should  be  chosen.  There  are 
still  many  points  in  regard  to  the  structure  of  the  skin  and  its 
appendages  which  appear  to  be  rather  doubtful,  owing  to  our 
insufficient  knowledge.  The  first  development  of  the  hair-fol- 
licle takes  place  at  the  end  of  the  third  or  beginning  of  the 
fourth  month,  and  it  originates  as  a  projection  downward  of 
the  cells  of  the  rete  mucosum.  It  is  seen  as  a  finger-shaped 
collection  of  rete  cells  surrounded  by  the  connective  tissue  of 
the  corium.  The  papilla  is  formed  later,  By  the  numerical 
increase  of  round  cells  the  follicle  is  enlarged,  and  the  external 
cells  are  pushed  sideward,  thus  forming  the  external  root- 
sheath.  The  origin  of  the  other  parts  of  the  hair  has  been 
already  described.  The  first  hairs  are  always  of  the  lanugo 
kind — that  is,  they  are  fine  hairs,  with  a  very  short  hair-folli- 
cle. In  certain  regions  the  hairs  always  remain  fine  ;  in  other 
parts  they  give  place  to  thicker  ones.  In  the  latter  case  a  pro- 
longation downward  of  the  external  root-sheath  takes  place. 
This  forms  the  hair-papilla.  The  papilla  of  the  first  hair  atro- 
phies, the  hair  falls  out,  and  its  place  is  occupied  by  a  thick 
hair.  The  permanent  hair  grows  to  a  certain  length,  which 
varies  in  different  persons  and  in  different  parts  of  the  body. 
If  a  hair  has  reached  its  proper  term  of  existence  it  falls  out 
and  is  replaced  by  a  new  hair,  which  grows  from  the  old 
papilla.  A  hair  ceases  to  be  produced  when  no  new  cells  are 
formed  in  the  hair-root.  The  last-formed  cells  become  con- 
verted into  the  hair  proper,  and  form  a  conical  or  knobbed  ex- 
tremity to  the  lower  end  of  the  hair-shaft. 

The  nails. — The  nail  is  merely  a  modification  of  the  epi- 
dermis, and  differs  from  the  stratum  corneum  only  in  being 
harder  and  firmer.  It  is  a  longish,  four-sided,  hard,  elastic, 
transparent,  dense,  flat  body,  situated  in  a  fold  of  the  skin  on 
the  dorsal  surface  of  the  terminal  phalanges  of  the  fingers  and 
toes.  It  is  slightly  curved  in  its  long  diameter,  the  convex  sup 
face  being  above  and  the  concave  below.  Its  posterior  and  two 
lateral  sides  are  connected  with  the  other  structures  of  the  skin ; 
the  anterior  side  is  free.  The  fold  of  skin  in  which  the  pos- 
terior and  two  lateral  surfaces  are  imbedded  increases  in  depth 
from  before  backward,  and  at  the  posterior  margin  is  continued 


294 


MANUAL    OF    HISTOLOGY. 


forward  for  a  short  distance  on  the  surface  of  the  nail.  This 
fold  of  skin  is  called  the  nail  fold,  and  the  tissue  upon  which 
the  nail  is  seated  is  termed  the  bed  of  the  nail.  That  part  of 
the  nail  imbedded  in  the  flesh  posteriorly  is  the  root  of  the  nail, 
and  the  remainder  its  body.  The  flesh  underlying  the  root — 
the  corium — is  called  the  matrix,  and  that  underlying  the  body 
of  the  nail  the  bed  of  the  nail  proper.  The  matrix  and  bed  of 
the  nail  proper  are  separated  by  a  more  or  less  convex  line,  gen- 
erally easily  seen  through  the  nail  and  known  as  the  lunula. 
The  bed  of  the  nail  is  composed  of  corium  and  rete  Malpighii 
tissue.  There  is  no  fat  in  its  subcutaneous  tissue.  The  rete 
here  dips  down  between  the  papillae  of  the  corium  as  in  other 
parts  of  the  skin.  The  papillae  in  the  matrix  project  forward, 
and  are  shorter  and  closer  together  than  in  the  bed  of  the  nail 


FIG.  124. — Transverse  section  of  the  nail  through  the  bed  of  the  nail  proper:  o,  nail ;  6,  loose  cor- 
neous layer  beneath  it :  c,  mucous  layer  :  rf,  transversely  divided  nail  ridces :  e.  nail-fold  without  papillae  ; 
/,  the  horny  layer  of  the  nail-fold  which  has  pushed  forward  on  the  nail ;  0,  papillae  of  the  skin  of  the 
finger. 

proper.  In  this  latter  structure  the  papillae  also  project  for- 
ward (Fig.  124,  d)  and  increase  in  length  as  the  free  margin  of 
the  nail  is  approached.  The  rete  Malpighii  covers  the  papillae 
of  the  nail,  forming  cones,  which  fill  the  space  between  the 
papillae.  In  the  bed  of  the  nail  proper  the  transition  from  rete 
cells  to  horny  cells  is  very  rapid,  whilst  in  the  matrix  it  is 
gradual.  Consequently,  this  portion  of  the  nail  is  softer  than 
the  other.  It  is  from  the  matrix  that  the  nail  is  formed,  and 
from  the  corneous  cells  of  the  body  of  the  nail  that  the  nail  is 
made  thicker.  The  soft  cells  are  directed  forward  and  become 
more  horny  as  they  advance.  The  under  surface  of  the  nail- 
fold  covering  the  posterior  part  of  the  nail  is  provided  with 
epidermis,  which  is  continued  forward  a  short  distance  on  the 
upper  surface  of  the  nail. 


THE    SKIN.  295 

The  tissue  of  the  nail  is  nourished  by  blood  from  the  bed  of 
the  nail  and  from  the  nail-fold.  Nails  grow  more  rapidly  in 
children  than  in  adults,  and  more  rapidly  in  summer  than  in 
winter.  The  rapidity  of  growth  varies  according  to  the  person 
and  the  particular  nail.  The  rate  of  growth  in  individual  nails 
can  be  learned  by  observing  the  rate  of  progress  toward  the  free 
margin  of  the  white  spots  seen  on  nails. 

The  nail  begins  to  form  in  the  third  month  of  intra-uterine 
life  as  a  fold  covered  with  a  layer  of  embryonic  epidermic  cells. 
In  the  fourth  month  a  layer  of  new  cells,  which  afterward  be- 
come the  horny  cells  of  the  nail,  appear  between  the  rete  Mal- 
pighii  and  the  embryonic  epidermic  corpuscles.  At  the  fifth 
month  the  epidermic  covering  disappears  and  the  nail  lies  ex- 
posed. Between  the  sixth  and  eighth  months  the  nails  are 
somewhat  firm,  but  do  not  quite  extend  to  the  ends  of  the 
fingers.  At  the  eighth  month  the  nails  are  well  developed  and 
extend  to  the  extremities  of  the  fingers. 

For  the  .microscopical  study  of  the  horny  part  of  the  nail, 
sulphuric  acid,  or  caustic  soda,  or  potash  must  be  employed  to 
soften  the  corpuscles.  For  the  other  structures  of  the  nail  no 
special  procedure  is  necessary. 


BIBLIOGRAPHY. 

WAGNER.     Miiller's  Archiv.     1852. 

MEISSNER.     Beitrage  z.  Anat.  u.  Phys.  d.  Haut.     Leipzig,  1853. 

OEHL,  E.     Annali  univ.  di  med.     1857. 

KRAUSE.     Die  term.  Korp.  d.  einf.  Sens.  Nerven.     Hannover,  1860. 

SCHROEN.     Contrib.  alia  anat.  fisiolog.  e  patholog.  della  cute  umana.    Torino,  1865. 

AUPPHAMEU.     Wurzburger  Verhandlungen.     Band  I.     1809. 

TUOMSA.     Arch.  f.  Derrnat.     1873. 

LOTT.     Ueber  den  feineren  bau  u.  die  phys.  Regeneration  des  Epithels.     Leipzig, 

1874. 

THIN.     Journal  of  Anat.  and  Phys.     Vol.  VIII.     1874. 
HEYNOLD.     Ueber  die  Knaueldriisen  des  Menschen.     Virchow's  Archiv.     Bd.  LXI. 

1874. 

UNNA,  P.     Archiv  f.  mikrosk.  Anat.     XII.     1876. 
FISCHER,  E.     Ibid. 

RAVOGLI.     Med.  Jahr.    Wien.     H.  I.     1879. 
RANVIER.     La  France  medicale.     January,  1880. 


CHAPTER  XIX. 

THE    CENTRAL,  NERVOUS  SYSTEM. 
BY  R.  W.  AMIDON,  M.D.,  NEW  YORK  CITY. 

THE  spinal  dura  mater  is  a  serous  membrane.  Its  structure 
from  without  inward  is :  first,  loose  connective  tissue ;  then  dense 
fibrous  tissue ;  lastly,  a  layer  of  lymph-vessels  and  endothe- 
lium.  If  one  tears,  with  forceps,  a  shred  from  the  outer  surface 
of  the  dura  mater,  fresh  or  hardened,  stains  with  hsematoxylon, 
teases,  and  examines  in  glycerine,  there  is  seen  a  loose  network 
of  connective- tissue  bundles  containing  free  and  fixed  connec- 
tive-tissue cells,  blood-vessels,  minute  nerves,  and  some  fat- 
cells.  This  layer  is  continuous  with  the  loose  adipose  tissue 
which  normally  surrounds  the  dura  mater.  The  denser  tissue 
next  in  order  may  be  treated  in  the  same  way,  and  perhaps  a 
few  spindle-shaped  connective-tissue  cells  and  elastic  fibres 
may  be  isolated. 

On  transverse  section,  however  (a  very  difficult  thing  to 
make,  by  the  way),  the  bulk  of  the  membrane  is  seen  to  be  a 
dense  mass,  0.5 — 1.0  mm.  thick,  composed  of  longitudinal  and 
horizontal  connective-tissue  bundles,  interspersed  here  and 
there  with  elastic  fibres.  In  this  layer  blood-vessels  and  nerves 
are  very  scanty  and  small. 

Next,  immerse  a  piece  of  dura  mater,  as  fresh  as  possible, 
in  a  one  per  cent,  solution  of  nitrate  of  silver.  Leave  it  for  sev- 
eral hours,  and  then  expose  it  for  a  few  minutes  to  the  sunlight. 
When  a  brown  tint  is  developed  on  the  inner  surface,  remove 
it,  wash  it  in  distilled  water,  and  strip  off  the  internal  surface 
with  forceps. 

The  shreds  of  tissue  thus  obtained  show  beautifully  the 
structure  common  to  all  serous  membranes  :  first,  a  delicate  en- 
dothelial  layer  (see  Fig.  125),  consisting  of  fiat,  unequal,  irreg- 
ularly shaped  cells,  most  of  which  are  furnished  with  large, 


THE    CENTRAL    NEKVOUS    SYSTEM.  297 

round  nuclei ;  here  and.  there  are  seen  stomata  marked  by  an  ag- 
gregation of  nuclei,  which  are  all  located  at  the  edge  of  the  cells 
surrounding  a  stoma  ;  secondly,  irregularly  disposed  lymph- 
spaces  and  vessels.  The  lymph-spaces  appear  as  irregular, 
transparent  patches  lying  just  under  the  endothelium,  and 
the  lymph-vessels  are 
seen  as  varicose  chan- 
nels, which  begin  by 
a  blind  extremity,  an-  , 
astomose  freely,  re- 
ceive tributaries,  and, 
iinally,  empty  by  a 
constricted  orifice 
called  a  stoma.  Their 

'     "  — ^- — *""  "  e, 

WallS      are      in      places  FIG.  ISS.— Diagram  representing  the  internal  surface  of  the 

i-i   •          1-4.  fi-  dura,  mater  treated  with  nitrate  of  silver.     Shows  endothelium 

Him,     DUG    more    Olien  with  nuclei  and  intercellular  masses  of  protoplasm  and  a  lymph- 

,  -i   .    -i  -,  ,  channel,   L.c.,  lined  by  delicate  endothelial  cells,  which  termi- 

IlllCK       anOL       11'regUlar  nates  at  S,  an  opening  called  a  stoma  about  which  is  an  aggre- 

«  ,  -,  .  gation  of  nuclei,     x  300. 

from  the  aggregation 

of  masses  of  protoplasm  along  the  sides.  The  capillary  lymph- 
atic radicles  are  lined  by  a  very  delicate  endothelial  layer, 
which  can  only  be  demonstrated  in  completely  successful  sil- 
ver preparations.  Some  are  seen  to  contain  lymph-corpuscles, 
others  are  found  empty. 

The  spinal  arachnoid  is  also  a  serous  membrane,  much  more 
delicate,  however,  than  the  dura  mater.  Its  extreme  thinness 
allows  it  to  be  examined  in  the  fresh  state  or  stained  by  car- 
mine or  hsematoxylon.  It  is  seen  to  be  essentially  a  large- 
meshed  connective-tissue  network,  containing  many  elastic 
fibres.  Good  silver  preparations  demonstrate  an  endothelial 
coat  and  a  lymph  system  similar  to,  but  more  delicate  than 
that  of  the  dura  mater.  It  is  doubtful  whether  blood-vessels 
exist  in  the  arachnoid  in  its  normal  state. 

The  spinal  pia  mater  consists  of  a  small  amount  of  connec- 
tive tissue,  holding  together  a  vascular  plexus.  It  is  firmly 
adherent  to  the  cord,  dips  into  all  its  fissures,  and  is  intimately 
connected  and  continuous  with  the  connective-tissue  frame- 
work of  the  cord.  The  pia  mater  is  best  studied  by  means  of 
fresh  specimens  stained  in  hsematoxylon,  as  this  demonstrates 
beautifully  the  different  coats  of  the  small  vessels. 

The  spinal  fluid  should  be  clear,  and  contain  only  a  few 
lymph-corpuscles  ;  but  it  usually,  when  examined  post-rnor- 


298  MANUAL    OF    HISTOLOGY. 

tern,  contains  some  blood-corpuscles  and  swollen  epithelial 
cells. 

General  histology  of  tlie  spinal  cord. — The  spinal  cord  is 
composed  of  connective  tissue,  blood-vessels,  nerve-structures, 
and  epithelium. 

The  connective-tissue  framework  or  neuroglia  of  the  cord 
is  constructed  as  follows :  At  tolerably  regular  intervals  the 
pia  mater  at  the  periphery  of  the  cord  sends  off  prolonga- 
tions which  form  septa,  dividing  the  white  substance  into  a 
large  number  of  prisms  (base  outward).  From  each  of  these 
septa  smaller  branches  spring,  forming  a  delicate  network,  or 
stroma,  which  encloses  the  nerve-fibres.  Generally  one,  but 
sometimes  two  or  more  fibres  are  contained  in  the  same  mesh. 

At  the  points  of  junction  of  these  ultimate  fibres  are  seen, 
here  and  there,  small  branching  cells>  the  so-called  spider-  or 
neuroglia- cells.  This  fibrous  structure  reaches  to  the  central 
gray  matter  and  penetrates  it  by  very  delicate  processes,  which 
chiefly  accompany  the  nerve-fibres. 

Three  large  prolongations  of  pia  mater  are  of  constant  oc- 
currence, viz.,  the  posterior  median  septum  and  a  less  complete 
septum  on  either  side,  dividing  the  posterior  column  into  two  ; 
the  larger,  anterior,  or  column  of  Burdacli /  and  the  smaller, 
posterior,  or  column  of  Goll.  The  connective-tissue  elements 
are  best  brought  out  by  hsematoxylon. 

The  blood-vessels  of  the  cord  are  derived  from  its  pia  mater, 
follow  its  prolongations,  and  are  most  numerous  in  the  gray 
matter,  especially  that  of  the  anterior  horns.  In  transverse 
sections  there  will  be  seen  a  clear  space  about  all  the  blood- 
vessels. This  is  the  perivascular  space  or  lymph-channel,  in 
which  all  the  blood-vessels  are  contained.  During  life  these 
sheaths  probably  serve  a  double  purpose:  an  auxiliary  nutri- 
ent function  by  lymph-circulation  ;  and  a  means  of  accommo- 
dating the  ever-varying  degrees  of  vascular  distention.  In 
some  diseases  they  become  enormously  dilated.  They  are  all 
connected  with  the  space  between  the  pia  mater  and  the  cord, 
and  an  injection  forced  into  this  space  will  follow  the  blood- 
vessels for  long  distances.  These  perivascular  spaces  are  also 
said  to  be  lined  with  endothelium. 

The  vessels  of  the  cord  present  no  other  peculiarities.  Their 
structure  is  best  brought  out  by  the  use  of  a  dilute  hjematox- 
ylon  solution,  or  by  the  slow  carmine  staining.  The  perivas- 


THE    CENTRAL    NERVOUS    SYSTEM.  299 

cular  canals  may  be  more  clearly  demonstrated  by  forcing  a 
colored  gelatine  injection  at  any  point  under  the  spinal  pia 
mater — care  being  taken,  if  the  cord  is  cut,  to  secure  the  ends 
of  the  sections  by  ligatures. 

Nerve  elements  of  the  cord. — The  consideration  of  the  ner- 
vous elements  of  the  cord  will  now  be  taken  up  in  a  general 
way,  and  the  peculiarities  of  different  regions  explained  later. 

The  white  substance  of  the  cord  contains,  besides  the  blood- 
vessels and  neuroglia  already  mentioned,  myelinic  nerve-fibres 
of  different  sizes.  These  fibres  pursue  a  vertical  course,  with 
the  exception  of  those  forming  the  root-radicles  and  commis- 
sures. 

On  examination  with  a  low  power,  the  white  substance,  in  a 
transverse  section  stained  with  carmine,  seems  to  be  a  collec- 
tion of  minute  rings,  each  with  a  red  dot  in  the  centre.  More 
highly  magnified,  the  transverse  section  of  a  nerve-fibre  appears 
as  a  delicate,  rather  irregular  circle,  on  the  circumference  of 
which,  in  some  cases,  are  seen  nuclei  resembling  those  of  the 
sheath  of  Schwann,  but  which  are  really  nuclei  of  the  neurog- 
lia. Next  comes  a  broad  ring  of  colorless,  transparent  mate- 
rial, the  medullary  or  myelinic- sheath,  which  very  often  ex- 
hibits concentric  lamination.  Lastly,  usually  in  the  centre,  is 
seen  the  solid  axis-cylinder. 

When  these  fibres  pursue  a  more  or  less  horizontal  direc- 
tion they  give  the  appearance  of  broad,  clear  bands  traversed 
by  longitudinal  red  fibres  (axis- cylinders).  The  myelinic  fibres 
average  about  5  yu-1  in  diameter.  Fibres,  when  isolated  by 
teasing,  present  the  varicose  aspect  of  myelinic  nerve-fibres, 
which  lack  the  sheath  of  Schwann.  To  demonstrate  this  they 
are  best  treated  when  in  the  fresh  state  by  osmic  acid  (see  p. 
114),  the  result  being  a  black  myelinic  sheath  and  brownish 
axis-cylinder. 

The  gray  matter  is  composed  of  nerve-cells,  medullated  and 
non-medullated  nerve-fibres,  and  an  amorphous  matrix.  The 
most  striking  elements  are  the  cells  of  the  anterior  horns. 
These,  whether  teased  from  specimens  fresh  or  hardened  in 
chromic  acid,  or  whether  examined  in  sections,  always  present 
the  same  general  appearance.  They  are  large,  multipolar  cells, 
having  a  slightly  granular,  protoplasmic  body,  a  large,  oval 

1  /*  —  micromillimetre  =  roVo  millimetre. 


300  MANUAL    OF    HISTOLOGY. 

nucleus,  and  a  round  nucleolus.  These  cells  are  polyhedral  in 
form,  as  is  shown  by  the  fact  that  sections  made  in  all  direc- 
tions give  them  the  same  pyramidal  or  polygonal  outline.  In 
nearly  all  the  large  cells  there  is  in  some  part  of  the  body  an 
aggregation  of  granules,  which  are  often  distinctly  pigmented, 
giving  the  appearance  of  a  heap. 

Striations  of  the  body  have  been  frequently  described  and 
depicted  (Schultze,  Schmidt,  etc.),  and  this  appearance  has 
been  attributed  by  some  to  plications  of  a  very  delicate  invest- 
ing membrane,  by  others  to  ex- 
pansions of  the  ultimate  nervous 
fibrillse,  of  which  the  axis-cyl- 
inder was  thought  to  be  com- 
posed. The  motor  cells  average 
about  40  fji.  in  diameter.  The 
cell -processes  vary  in  number. 
Most  of  them  are  bifurcating. 
One,  however,  connected  with 
nearly  every  cell,  can  be  fol- 
lowed for  a  long  distance  with- 
out dividing,  and  when  the  cell 
is  situated  near  the  anterior 

FIG.  126. — Diagram  of  a  motor-cell  from  the 

anterior  horn  of  a  human  cord  in  the  cervical  rOOtletS  this  prOCeSS  lomS  them 
enlargement,  x  800.  J 

and  acquires  a  myelinic  sheath. 

This  is  called  the  axis-cylinder  process.  The  branching  pro- 
cesses are  called  the  protoplasmic  processes,  and  are  supposed 
by  some  to  freely  anastomose  with  those  of  other  cells.  This 
anastomosis,  if  it  exist  at  all,  is  very  delicate,  and  difficult  of 
demonstration. 

A  certain  number  of  the  cells  of  the  anterior  horns,  espe- 
cially those  located  in  the  lateral  region  of  the  cornua,  present 
an  elongated,  fusiform  aspect,  and  appear  to  have  but  two 
processes.  The  nerve-cells  in  the  posterior  horns  are  of  an 
elongated  oval  or  fusiform  shape,  their  long  diameter  corre- 
sponding in  direction  with  that  of  the  posterior  horn.  They  are 
very  much  smaller  than  the  anterior  cells,  and  less  numerous. 
Their  average  diameter  is  about  15  p,.  They  are  seldom  seen 
to  have  processes. 

The  myelinic  nerve-fibres  of  the  gray  matter  are  seen  prin- 
cipally in  the  anterior  horns,  and  converging  from  the  cell- 
groups  to  form  the  anterior  root-radicles.  Here  and  there  fibres 


THE    CENTRAL    NERVOUS    SYSTEM.  301 

appear  in  transverse  section,  which,  singly  or  in  bundles,  pur- 
sue a  longitudinal  direction. 

Amyelinic  fibres  are  found  everywhere  in  the  gray  matter 
pursuing  various  courses.  The  gray  commissure  is  composed 
almost  completely  of  amyelinic  fibres  connecting  the  lateral 
gray  masses. 

Besides  the  above-described  elements  the  gray  substance 
seems  to  have  a  structureless  or  slightly  granular  matrix,  in 
which  the  other  elements  are  embedded.  In  the  study  of  the 
spinal  gray  matter  osmic  acid  and  carmine  preparations  are  by 
far  the  most  useful,  although  much  is  to  be  learned  by  the  ex- 
amination of  fresh  specimens  teased  in  serum.  To  study  the 
cells,  cut  out  a  piece  from  the  anterior  horn  of  a  fresh  cord 
and  tease  in  serum.  A  preliminary  treatment  with  osmic  acid 
or  ammoniacal  carmine  is  sometimes  advantageous. 

The  epithelium  of  the  spinal  cord  lines  the  central  canal. 
The  most  internal  layer  is  of  the  cylindrical,  ciliated  variety. 
On  account  of  the  difficulty  in  obtaining  fresh  specimens  the 
cilia  are  never  seen  in  the  human  cord,  though  they  undoubt- 
edly exist.  The  epithelial  cells,  as  they  do  exist  in  the  human 
cord,  have  a  square  base,  taper  to  a  slender  thread  toward 
the  apex,  which  penetrates  the  layer  of  young,  round  epithe- 
lial cells,  and  is  lost  in  the  granular  central  gray  matter.  The 
cells  of  the  second  layer  are  round,  granular,  and  thickly 
crowded. 

The  sub  epithelial  tissue,  for  some  distance  around  the  cen- 
tral canal,  consists  of  embryonal  cells  in  a  granular  matrix. 

The  central  canal  *  has  no  constant  shape,  varies  greatly  in 
size,  and  is  often  choked  with  desquamated  epithelium.  Its 
position,  as  its  name  indicates,  is  in  the  middle  of  the  gray 
commissure,  on  a  line  passing  between  the  anterior  fissure  and 
posterior  septum.  The  general  features  of  the  spinal  cord  hav- 
ing been  pointed  out,  the  peculiarities  of  different  regions  will 
now  be  shown. 

Special  study  of  the  different  portions  of  the  cord. — The 
cord  will  be  studied  from  below  upward.  The  mode  of  study 
will  mainly  be  by  sections  made  after  Clarke's  method.  The 
cord,  after  slitting  the  dura  mater  with  the  scissors  up  the 
front  and  back,  is  cut  in  segments  3  ctm.  long,  which  adhere 

1  Sometimes  double.     See  Seguin:  Am.  Jour.  Med.  Sci.,  p.  427.     1872. 


302  MANUAL    OF    HISTOLOGY. 

to  the  undivided  dura  mater.  Thus  prepared  it  is  suspended 
in  Muller's  fluid  (see  p.  15),  or  dilute  chromic  acid  (see  p. 
14),  until  hardened.  The  segments  are  then  embedded  in 
a  microtome  (see  p.  16),  and  horizontal,  transverse  sections 
made.  These  are  washed  in  distilled  water  and  stained  with 
carmine  or  hsBmatoxylon  (see  p.  23).  A  few  minutes'  immer- 
sion in  alcohol  previous  to  this  manipulation  makes  the  tissues 
take  the  coloring  more  quickly.  After  staining  and  washing, 
dehydrate  the  sections  with  alcohol  and  absolute  alcohol,  make 
transparent  with  oil  of  cloves,  and  mount  in  Canada  balsam  or 
dammar  varnish  (see  p.  23). 

Hidden  in  the  cauda  equina  is  found  the  filum  terminate, 
which  is  the  end  of  the  cord.  Sections  near  its  end  exhibit  lit- 
tle of  the  structure  of  the  cord.  At  a  point  where  it  is  1.5  mm. 
in  diameter  it  presents  the  appearance  of  a  peripheral  nerve, 
except  that  it  has  an  opening — the  central  canal — in  its  centre. 
Its  transverse  section  shows  a  collection  of  large  and  small 
myelinic  nerve-fibres  pursuing  a  vertical  direction. 

A  little  higher  up,  where  the  filum  measures  2  mm.  in  diam- 
eter, there  is  little  difference,  except  that  the  central  canal  is 
nearer  the  surface  (anterior)  and  surrounded  by  a  small  amount 
of  gray  matter.  Now  and  then  there  are  seen  small,  oval  nerve- 
cells  in  the  region  posterior  and  external  to  the  central  canal. 
A  little  higher  still,  where  the  filum  is  3  mm.  in  transverse 
and  2  mm.  in  antero-posterior  diameter,  back  of  the  central 
canal  on  each  side,  where  the  future  posterior  horn  is  to  be, 
there  is  a  small  collection  of  spindle-shaped  cells. 

Sections  from  a  region  a  little  above  this  present  an  entirety 
different  picture.  The  gray  substance  is  here  much  more  devel- 
oped and  occupies  the  larger  part  of  the  section.  It  is  divided 
into  a  club-shaped  anterior  horn,  containing  a  few  large  poly- 
hedral cells,  and  a  posterior  horn  which  is  rounded  and  formed 
of  peripherally  directed  nerve-fibres  and  oblong  nerve-cells. 
From  this  point  up  sections  gradually  become  more  circular 
arid  develop  more  and  more  a  resemblance  to  the  structure  of 
the  cord,  until,  at  a  point  where  the  sections  are  about  3.5  mm. 
in  diameter,  the  anterior  fissure  and  posterior  septum  become 
well  marked.  The  anterior  horns  contain  few  cells,  and  the 
fibres  emanating  from  them  pursue  a  very  oblique  course  down- 
ward through  the  anterior  columns. 

From  the  lateral  gray  matter  arise  bundles  of  nerve-fibres 


THE    CENTRAL    NERVOUS    SYSTEM. 


FIG.  127.— Three  sections 
of  the  filum  terminate:  «,  its 
transformation  into  the  coccy- 
geal  nerve ;  6,  section  higher 
up  before  the  giving  off  of  the 
last  sacral  filaments;  c,  its 
commencement. 


which  curve  around  the  posterior  horn,  and,  meeting  similar 
h'bres  from  the  posterior  columns,  together  form  the  posterior 
nerve-root.  These  two  bundles  form  an  arciform  structure  sur- 
rounding the  round  extremity  of  the  posterior  horn.  (See  Fig. 
127.)  The  gray  commissure  occupies  one-third  the  diameter  of 
the  cord.  The  central  canal  is  large,  slit- 
like,  and  antero-posterior  in  direction.  To 
summarize  then,  there  seems  to  be  in  the 
filum  terminale,  especially  its  lower  por- 
tion, a  preponderance  of  the  posterior  or 
sensory  part  of  the  cord. 

About  two  centimetres  from  the  end  of 
the  cord  nearly  the  same  picture  is  pre- 
sented. The  transverse  section  is  circular 
and  about  6  mm.  in  diameter.  Many  large 
nerve-cells  appear  at  the  outer  side  of 
the  anterior  cornua,  mostly  at  their  junc- 
tion with  the  posterior  horns.  Fibres  from 
this  cell-group,  instead  of  running  a  direct  course,  curve 
backward  and  inward  (see  Fig.  127),  then  run  forward  and 
emerge  from  the  anterior  horns.  Many  oval  cells  appear  in 
the  posterior  horns,  which  now  reach  the  surface  of  the  sec- 
tion, and  the  posterior  roots  begin  to  show  their  origin  from 

the  posterior  columns  and  horns. 

In  the  lumbar  enlargement  trans- 
verse sections  have  a  circular  shape. 
(See  Fig.  128.)  The  white  substance 
here  predominates,  and  has  but  one 
peculiarity,  which  will  be  noticed  in 
greater  or  less  prominence  through- 
out the  remainder  of  the  cord.  At 
the  bottom  of  the  anterior  fissure  is  a 
broad  band  of  white  substance  called 
the  white  commissure.  This  is  formed 
of  myelinic  nerve-fibres,  which  pursue 
a  course  from  the  base  of  the  anterior 
horn  of  one  side,  forward,  across  the 
median  line  and  downward  to  join  the 
anterior  column  of  the  opposite  side  at  a  lower  level.  (See 
Fig.  129.)  The  anterior  horns  in  the  lumbar  region  are  large 
and  square,  as  are  also  the  cells  contained  in  it.  TJie  gray 


FIG.  128. — Three  diagrams  show- 
ing the  relations  of  gray  and  white 
matter  in  different  regions  of  the  cord: 
«.  lumbar  enlargement ;  6,  mid-dorsal 
region  ;  c,  cervical  enlargement. 


304 


MANUAL    OP    HISTOLOGY. 


commissure  is  narrow,  and  the  central  canal  has  its  long  diam- 
eter placed  transversely  to  the  cord. 

Transverse  sections  in  the  dorsal  region  are  circular  and 
8  mm.  in  diameter.  The  white  commissure  is  thin,  otherwise 
the  same  structure  as  in  the  lumbar  region  is  observed.  The 
anterior  horns  are  narrow  and  sparsely  filled  with  rather  small 
multipolar  cells.  JN~o  continuous  tracts  of  nerve-fibres  can  be 
traced  through  the  anterior  columns,  as  their  course  is  so  oblique 
(downward)  as  to  give  almost  a  transverse  section  of  the  bun- 
dles. The  posterior  horns,  just  behind  the  gray  commissure, 
are  swollen  out,  and  contain  a  number  of  large  nerve-cells — 
some  multipolar,  some  oval.  They  approach  the  type  of  the 
cells  in  the  posterior  horns.  This  collection  of  cells  is  called  the 
column  of  Clarke. 

Transverse  sections  in  the  cervical  enlargement  measure 
about  14  mm.  The  antero-posterior  diameter  is  about  11  mm. 
The  white  commissure  in  this  region  presents  about  the  same 
characteristics  as  in  the  lumbar  region.  The  anterior  horns  are 

fan- shaped  ;  the  anterior  roots 
curve  forward,  outward,  and 
downward.  The  central  canal  is 
triangular.  The  posterior  horns 
are  slender,  and  contain  a  few 
small  nerve-cells.  The  posterior 
roots  are  also  more  intimately 
connected  with  the  posterior 
horns  than  lower  down. 

In  the  upper  cervical  region 
the  gray  matter  assumes  more 
the  shape  of  the  dorsal  gray 
matter.  In  the  lateral  region,  at 
the  junction  of  the  anterior  and 
posterior  horns,  longitudinal  bun- 
dles of  myelinic  nerve-fibres  begin  to  appear.  These  bundles 
curve  over  (see  Fig.  129),  and  pass  rather  obliquely  upward 
and  outward  through  the  lateral  columns,  emerging  nearer  the 
posterior  than  the  anterior  horns.  They  are  joined  by  fibres 
curving  back  from  the  cells  of  the  anterior  horns,  and  also 
emanating  from  the  central  gray  matter.  In  this  structure  is 
seen  the  first  appearance  of  the  spinal  portion  of  the  spinal 
accessory  root-fibres.  The  longitudinal  bundles  mentioned 


FIG.  129. — Diagram  of  transverse  section  of 
the  cord  in  the  upper  cervical  region,  showing 
coarse  connective-tissue  reticulum  in  left  half 
of  diagram,  commencing  decnssation  of  the 
lateral  columns  across  the  base  of  the  anterior 
horn  into  the  opposite  anterior  column,  taking 
the  place  of  the  anterior  commissure  lower 
down,  and  the  root  of  the  spinal  accessory,  11 : 
A.R.  =  anterior  root ;  P.R.  =  posterior  root. 
In  this  figure  and  in  others  small  crosses  must 
be  understood  as  nerve-cells. 


THE    CENTRAL    NERVOUS    SYSTEM. 


305 


evidently  come  from  cells  of  the  anterior  horns  lower  down. 
Some  of  the  fibres,  passing  back  from  the  anterior  horns  to  join 
the  root,  are  seen  to  arise  directly  from  the  motor  cells. 

In  taking  leave  of  the  cord,  the  introduction  of  a  diagram1 
showing  its  regional  anatomy,  looked  at  from  a  physiological 
standpoint,    is    deemed   ad- 
vantageous.    It  will  enable  p 
the  microscopist  to  properly 
record  localized  lesions. 

In  studying  the  spinal 
cord  by  means  of  horizon- 
tal transverse  sections,  it  is 
of  the  utmost  importance, 
particularly  in  pathological 
cases,  to  know  which  is  the 
right  or  left  side,  and  whe- 
ther one  is  looking  at  the 
upper  or  under  surface  of  a 
section.  Of  so  much  impor- 
tance is  this  knowledge, 
that  some  means  must  be 
employed  to  acquire  it. 

One  of  the  best  means  is  a  method  devised  by  Dr.  E.  C. 
Seguin,  and  published  in  the  translator's  note  appended  to 
Schultze'  s  article  on  the  spinal  cord,  in  the  American  translation 
of  Strieker's  "  Histology,"  p.  647.  He  there  recommends,  be- 
fore placing  the  segment  of  the  cord  in  the  microtome,  that  a 
slight  longitudinal  incision  be  made  in  the  right  lateral  column. 
By  this  means  all  the  sections  have  a  nick  in  the  right  lateral 
column,  and  can  easily  be  placed.  This  method,  however,  has 
many  drawbacks.  One  is  that  it  is  a  process  easily  forgotten 
during  the  manipulations.  Another  more  serious  drawback  is 
the  fact  that,  make  the  incision  slight  as  you  can,  the  resulting 
nick  often  causes  extensive  fissures  and  crumbling  of  the  lateral 
column  or  whole  section,  especially  in  pathological  or  over- 
hardened  specimens. 

The  requirements  by  the  new  method  are  two :  1st,  the 
sections  must  be  nearly  horizontal ;  and  2d,  they  must  be  suf- 


FIG.  130. — Diagram  of  transverse  section  of  the 
spinal  cord  :  A,  anterior  median  fissure ;  P,  posterior 
median  septum ;  1,  columns  of  Goll ;  2,  columns  of 
Burdach  ;  8,  direct  cerebellar  column ;  4,  crossed  pyra- 
midal column  ;  5.  lateral  column  ;  6,  anterior  funda- 
mental column ;  7,  direct  pyramidal  column  ;  8,  pos- 
terior gray  horns ;  9,  anterior  gray  horns ;  stippled 
part,  gray  matter ;  shaded  part,  sesthesodio  system ; 
unshaded  part,  kinesodic  system. 


1  Dr.  E.  C.  Seguin :  Lectures  on  Localization,  in  N.  Y.  Medical  Record,  April  27, 
1878,  p.  323. 


306 


MANUAL    OF    HISTOLOGY. 


ficiently  well  stained  and  transparent  to  demonstrate  the  con- 
stituent parts  of  myelinic  nerve-fibres.  The  mode  of  determi- 
nation depends  entirely  on  the  fact  that  the  anterior  roots 
pursue  an  obliquely  descending  course  .through  the  anterior 
columns,  and  for  this  reason  horizontal  sections  cut  the  ante- 
rior rootlets  obliquely.  (See  Fig.  131.) 

What  is  the  natural  inference  to  draw  from  this  fact  \  It  is 
this  :  let  the  reader  look  at  the  upper  surface  of  a  transverse 
section  of  the  spinal  cord  and  bring  the  anterior  roots  into  the 
field  ;  that  is,  let  him  look  down  the  anterior  column.  He 
readily  perceives  that  the  central  ends  of  the  anterior  root- 
fibres  are  nearer  his  eye  than  the  peripheral  ends.  He  sees 
that  while  the  central  ends  are  at  the  focus,  the  peripheral 
ends  are  beyond  the  focus,  and  he  needs  to  bring  the  eye  nearer 
to  define  them.  This  nearing  the  focus  also  gives  the  fibre- 
bundle  an  apparent  peripheral  motion,  while  increasing  the 
focal  distance  causes  an  apparent  central  motion. 

The  application  of  this  method  to  a  chance  section  is  easy. 

Suppose  we  examine  the  anterior 
columns  of  a  section  and  find  by 
focussing  that  the  central  ends  of 
the  anterior  root-fibres  are  farther 
from  the  eye  than  the  peripheral 
ends.  We  will  immediately  know 
we  are  looking  up  the  cord  or  at 
the  under  surface  of  the  section. 
Now,  all  it  is  necessary  to  do  is 
to  turn  over  the  section,  either  in 
your  mind  or  on  the  slide,  and  put 
the  anterior  horns  forward.  The 
section  is  then  in  position. 

In*  sections  of  the  cord  where 
the  anterior  roots  do  not  show,  the 
posterior  roots  may  be  used  in  a  similar  way,  as  they,  too,  pur- 
sue a  slightly  descending  course.  Their  use  is  not  so  easy,  as 
the  fibres  are  short  and  pursue  a  slightly  wavy  course.  In 
sections  or  fragments  of  sections,  where  neither  of  these  struc- 
tures avail,  a  study  of  the  course  of  the  fibres  in  the  anterior 
white  commissure  will  lead  to  detection.  These  fibres  pursue 
a  course  downward  and  across  the  median  line,  from  the  base  of 
one  anterior  horn  into  the  anterior  column  of  the  opposite  side. 


FIG.  131.— Diagram  of  vertical  section 
•of  human  cord  through  the  anterior  arid 
iposterior  columns  and  the  anterior  horns. 
It  is  intended  to  demonstrate  how  a  trans- 
verse, horizontal  section,  S,  cuts  the  an- 
terior nerve-roots  obliquely.  (From  Ar- 
•chives  of  Medicine,  August  1,  1879,  p.  70.) 


THE    MEDULLA   OBLONGATA. 


307 


In  sections  of  the  upper  cervical  region  the  spinal  accessory 
roots  may  be  made  use  of,  remembering,  however,  that  they 
pursue  a  course  obliquely  upward  through  the  lateral  columns. 

The  application  of  these  rules  to  the  medulla  will  be  pointed 
out  later  on. 


NOTE. — To  demonstrate  the  obliquity  of  the  anterior  rootlets,  find,  by  a  trans- 
verse section,  the  exact  direction  of  the  anterior  rootlets,  and  then  make  longi- 
tudinal sections  through  the  anterior  column  and  horn  on  this  line. 


THE  MEDULLA   OBLONGATA. 


In  the  upper  part  of  the  cervical  region  changes  take  place 
in  the  arrangement  of  the  elements  of  the  cord  transforming  it 
into  the  medulla  oblongata.  The  changes  are  as  follows  :  be- 
fore the  external  signs 
of  decussation  ap- 
pear, it  is  seen  that 
the  fibres  of  the  later- 
al columns  change 
their  vertical  course 
and  bend  forward  and 
inward.  This  fact  is 
demonstrated  by  the 
oblique  sections  of 
bundles  and  fibres.  A 
little  higher  these 
bundles  and  fibres 
can  be  traced  across 
the  gray  matter  be- 
hind the  anterior  horn 
into  the  opposite  an- 
terior column,  which  is  to  become  by  this  addition  the  anterior 
pyramid.  The  decussating  fibres  take  the  place  of  the  ante- 
rior commissure  lower  down,  and  the  fibres  pass  upward  and 
forward  across  the  median  line.  The  fibres  of  the  anterior 
columns  do  not  decussate  at  all,  but  give  way  to  and  mingle 
with  the  fibres  from  the  lateral  columns. 

The  shape  and  structure  of  the  anterior  horns  are  about  the 
same  as  lower  down.     The  posterior  horn  expands  suddenly  at 


FIG.  132. — Diagram  of  the  medulla,  pons,  etc.,  natural  size,  to 
show  the  direction  of  sections  for  displaying  the  different  nuclei 
and  roota :  ll/,  line  of  section  to  show  the  early  decnssation  of  the 
lateral  columns  and  spinal  accessory  tract;  11,  line  of  section  to 
show  the  spinal  accessory  tract  and  decussation  of  the  pyramids ; 
11  &  12,  region  of  the  spinal  accessory  and  hypoglossal ;  10,  pneu- 
mogastric;  9,  glosso-pharyngeal ;  8,  acoustic;  6  &  7.  abducens 
and  facial ;  5.  trigeminus ;  4,  patheticus  ;  3,  motor  oculi ;  c.  g., 
corpora  quadrigemina ;  c.  c.,  crua  cerebri. 


308 


MANUAL    OF   HISTOLOGY. 


its  peripheral  extremity  into  a  bulbous  termination  (see  Fig. 
133),  from  which  the  posterior  root  emerges.  The  central  gray 
matter  between  the  two  horns  is  traversed  and  intersected  by 
the  decussating  fibres  from  the  lateral  columns.  Numerous  pro- 
longations from  this  gray  matter  spread  out  into  the  lateral 
columns,  presenting  a  coarse  reticulum,  called  iheformatio 


FIG.  133.— Diagram  of  transverse  section  of 
human  medulla  below  external  decussation  of 
pyramids,  showing  bulbous  posterior  horns: 
F  R,  formatio  reticularis;  11,  spinal  accessory 
root  and  decussation  of  the  lateral  columns. 


FIG.  134. — Diagram.  Decussation  of  the  pyra- 
mids, shows  decussation  of  the  lateral  columns, 
the  swelling  of  the  posterior  horns,  the  shrink- 
age of  the  anterior  horns,  the  spinal  accessory 
root  11,  and  a  partial  decussation  of  the  posterior 
columns  behind  the  central  canal. 


reticularis.  The  gray  commissure  is  very  broad,  the  central 
canal  having  its  long  diameter  directed  antero-posteriorly. 

In  sections  at  the  decussation  of  the  pyramids  proper,  i.e., 
where  they  are  seen  to  decussate  externally,  a  slightly  different 
picture  is  presented.  The  lateral  columns  have  nearly  disap- 
peared, having  now  almost  all  entered  into  the  decussation, 
which  is  here  very  broad  (see  Fig.  134),  and  presents  a  peculiar 
zigzag  appearance  from  the  interweaving  of  bundles  of  fibres 
from  the  opposite  lateral  columns.  These  fibres,  after  curving 
around  the  anterior  columns  for  a  short  distance,  seem  to  dis- 
appear by  assuming  a  vertical  direction.  The  club-shaped  ex- 
tremities of  the  posterior  horns  remain,  while  the  rest  is  pushed 
back  into  the  posterior  columns,  and  contains  many  large  cells. 

The  anterior  horns  are  also  displaced  backward,  pushed 
back  by  the  anterior  columns  increased  in  size  by  the  addition 
of  the  lateral  columns.  Hence,  the  anterior  roots  have  a  longer 
path  through  the  anterior  columns  and  approach  the  type  of 
the  hypoglossal  nerve-roots  seen  a  little  higher  up.  (See  Fig. 
135.)  The  spinal  accessory  nerve  curves  out  and  back  from  the 
lateral  gray  matter  where  a  group  of  cells  is  situated. 


THE    MEDULLA    OBLONGATA. 


309 


Let  us  next  take  up  a  section  involving  the  lower  end  of 
the  olivary  body.  We  have  the  following  view  presented. 
The  section  is  slightly  cordiform.  (See  Fig.  135.)  The  decussa- 
ting fibres  at  the  base  of  what  remains  of  the  anterior  fissure, 
which  has  all  along  become  shallower,  now  forms  the  com- 
mencement of  the  rapke,  a  structure  which  extends  all  through 
the  rest  of  the  medulla  and  pons,  separating  the  two  motor 
tracts.  The  union  of  the  lateral  and  anterior  columns  now 
nearly  complete,  forms  the  anterior 
pyramids.  The  fibres  here  have  a 
general  vertical  direction,  except 
that  a  broad  band  which  emerges 
from  the  decussation  at  the  bottom 
of  the  anterior  fissure,  curves  around 
the  margin  of  the  anterior  pyramid, 
and  then,  sometimes  in  the  sub- 
stance, sometimes  at  the  surface  of 
the  medulla,  almost  completely  sur- 
rounds it,  the  bundle  becoming  lon- 
gitudinal on  the  posterior  surface. 
These  bear  the  name  of  the  arciform 
fibres.  The  rest  of  the  white  matter 
is  so  cut  up  as  to  render  it  hardly 
divisible  into  regions.  The  central  canal,  which  is  very  long 
antero-posteriorly,  has  almost  coalesced  with  the  gradually 
deepening  posterior  furrow  soon  to  become  the  fourth  ventricle. 

The  gray  matter  originally  in  the  cord  is  now  collected 
about  the  central  canal.  Anterior  and  external  to  the  central 
canal  there  is  a  small  group  of  multipolar  cells.  This  is  the 
remnant  of  the  anterior  horns,  which  have  been  continually 
crowded  back  by  the  accumulation  of  fibres  in  the  anterior 
pyramids.  These  cells  in  every  respect  are  similar  to  those  in 
the  anterior  horns.  Their  processes  give  origin  to  fibres  which 
course  forward  in  two  or  three  bundles  through  the  white 
matter  of  the  anterior  pyramids,  and  emerge  at  about  the 
junction  of  the  anterior  pyramids  and  the  lateral  white  mass. 

A  little  farther  back  in  the  gray  matter,  behind  the  central 
canal,  is  a  small  group  of  nerve-cells  the  remains  of  the  spinal 
accessory  nucleus,  from  which  a  few  fibres  run  in  a  straight 
course  outward  and  slightly  backward,  through  the  lateral 
white  matter.  Additional  collections  of  gray  matter  now  begin 


FIG.  135. — One  half  of  section  at  lower 
end  of  the  olives  :  11,  upper  spinal  acces- 
sory root ;  12,  lower  hypoglossal  roots. 


310  MANUAL    OF   HISTOLOGY. 

to  appear.  In  the  posterior  region  is  a  large  tract  (see  Fig.  135) 
containing  scattered  groups  of  many  small  cells  evidently  con- 
nected with  the  arcit'orm  fibres.  This  is  probably  a  part  of 
the  lower  origin  of  the  pneumogastric.  A  little  in  front  and 
external  to  this  is  a  small  group  of  larger  nerve-cells  which 
help  to  form  the  lower  sensory  origin  of  the  fifth  nerve.  Still 
farther  forward  in  the  lateral  region  is  a  large  collection  of 
multipolar  nerve-cells.  Although  this  group  is  traversed  in 
many  directions  by  fibres,  single  and  in  bundles,  still  it  seems 
to  give  rise  to  fibres  which  run  back  and  upward,  evidently  to 
curve  upon  themselves  and  join  the  peripheral  fibres  of  the 
spinal  accessory  root.  (See  Figs.  135  and  137.) 

Farther  forward  still  there  is  a  collection  of  small  cells 
arranged  in  a  wavy  line  (see  Fig.  135),  the  commencement  of  the 
olivary  nucleus.  Through  this  the  roots  of  the  hypoglossus 
all  pass.  Some  seem  to  be  lost  in  it,  others  appear  to  arise 
from  it,  but  this  is  probably  due  to  the  arrangement  of  roots 
often  seen  to  curve  into  the  nucleus  and  then  out  again.  As 
this  is  the  first  appearance  of  the  olivary  body,  it  will  be  well 
here  to  describe  it. 


THE  OLIVARY  BODY. 

The  olivary  nuclei  are  situated  in  the  medulla,  under  the 
oval  projections  on  its  anterior  surface  called  the  olivary  bodies. 
The  nucleus  consists  of  a  strip  of  gray  matter  arranged  in  gen- 
eral like. a  piece  of  fluting  folded  on  itself,  so  as  to  form  almost 
an  ellipse.  From  the  concavities  of  the  fold  on  either  side  pro- 
ceed bundles  of  fibres,  the  external  ones  joining  the  formatio 
reticularis,  the  internal  ones  passing  into  the  raphe.  Their 
connection  with  the  hypoglossal  roots  is  probably  not  im- 
portant. The  intimate  structure  of  the  olivary  fold  is  that  of  a 
dense  gray  matrix  holding  numerous  small  polyhedral  cells 
having  delicate  protoplasmic  processes. 

Let  us  now  go  a  trifle  higher  (see  Fig.  137),  and  observe  that 
in  sections  the  central  canal,  which  has  all  along  been  elongat- 
ing and  receding  backward,  now  opens  into  the  apex  of  the 
fourth  ventricle.  There  is  now,  therefore,  quite  a  deep  notch  in 
the  posterior  part  of  the  section,  covered  with  the  same  cylin- 
drical epithelium  which  lined  the  central  canal.  On  each  side, 


THE    OLIVARY    BODY. 


311 


and  in  front  of  the  bottom  of  the  fourth  ventricle,  lies  a  large 
group  of  multipolar  cells,  the  Jiypoglossal  nucleus,  from  which 
bundles  of  fibres  course  forward  through  the  olivary  body, 
which  is  here  much  enlarged  and  more  complex  than  in  the 
last  section.  On  the  inner  side  of  the  hypoglossal  roots  in 
the  olivary  region  is  an  elongated  mass  of  gray  matter  con- 
taining small  cells,  called  the  parolmary  nucleus.  There  is 
an  oval  group  of  fusiform  cells  at,  behind,  and  external  to 
the  hypoglossal  nucleus,  from  which  indistinct  and  broken 
bands  of  fibres  pass  outward  to  emerge  from  the  lateral  re- 
gion of  the  medulla.  This  constitutes  the  upper  spinal  acces- 
sory nucleus  and  root.  Behind  this  nucleus,  forming  the 


FIG.  136. — Diagram  showing  structure  of 
one  fold  of  the  olivary  nucleus :  C,  centripe- 
tal fibres ;  P,  peripheral  fibres,  x  64. 


FIG.  137. — One-half  transverse  section  of 
the  human  medulla  at  the  point  of  fusion  of 
the  central  canal  and  the  posterior  fissure  to 
form  the-fourth  ventricle  :  11,  spinal  acces- 
sory root ;  12,  hypoglossal  root ;  B,  raphe. 


eminence  on  each  side  of  the  fourth  ventricle,  is  a  large  mass 
of  gray  matter  containing  a  great  number  of  small  nerve-cells, 
which  also  seems  to  be  rather  indistinctly  connected  with 
the  spinal  accessory  root.  External  to  this  nucleus  is  a  con- 
tinuation of  the  collection  of  large  cells  seen  in  the  section 
lower  down,  the  lower  sensory  nucleus  of  the  fifth.  In  front 
of  the  spinal  accessory  root  is  seen  a  group  of  multipolar  cells 
not  so  large  as  in  preceding  sections.  The  peripheral  circular 
fibres  in  this  region  are  confined  to  the  anterior  and  external 
aspect  of  the  medulla,  and  are  still  seen  to  be  in  connection 
with  the  raphe  by  the  arcuate  fibres  which  traverse  obliquely 
the  intervening  nervous  tissue. 

From  this  point  to  the  middle  of  the  olives,  sections  differ 


312 


MANUAL    OF    HISTOLOGY. 


FlG.  138. — One-half  transverse  section  of  the 
human  medulla  through  the  middle  of  the  olives : 
4,  fourth  ventricle  ;  10,  pueumogastric  root ;  12, 
hypoglossal  root. 


little,  except  that  in  this  space  the  root-fibres  of  the  spinal 
accessory  seldom  appear,  although  figured  by  most  writers. 
The  region  formerly  occupied  by  the  spinal  accessory  nucleus 
contains  a  group  of  small  cells  which  form  part  of  the  pneu- 

mogastric  nucleus.  The  fibres 
between  this  nucleus  and  the 
point  of  exit  of  the  pneumo- 
gastric  root  run  so  obliquely 
upward,  that  no  direct  connec- 
tion between  them  can  be  traced. 
It  is  in  sections  at  the  mid- 
dle of  the  olives  that  the  pneu- 
mogastric  begins  to  appear  dis- 
tinctly. Most  of  its  fibres  seem 
to  be  connected  with  a  small 
group  of  cells  situated  in  the 

PTaV   matter,   at  the    lUnction  of 
O       y  <i 

the  funiculi  graciles  and  the 
restiform  body.  The  gray  mat- 
ter of  the  restiform  bodies  is  filled  with  small  cells  and  con- 
tains many  fibres  having  a  peripheral  direction  posterior  to  the 
pneumogastric  root — the  beginning  of  the  auditory  nucleus 
and  root.  The  olivary  body  here  reaches  its  highest  develop- 
ment and  greatest  dimensions. 

Behind  the  olivary  body  is  a  small  group  of  cells,  from 
which  scattered  fibres  pass  backward  and 
inward  toward  the  pneumogastric  nucle- 
us. But  most  of  them  are  lost  by  as- 
suming a  longitudinal  direction.  This  is 
probably  the  lower  facial  nucleus,  to  be 
described  farther  on.  The  arcif orm  fibres 
are  chiefly  confined  to  the  surface  of  the 
anterior  pyramids  and  the  olivary  bod- 
ies. The  fibres  of  the  raphe  pursue,  in 

.  -,.          ,.  Fio.   139.— One  -  half   trans- 

great  part,  an  antero-posterior  direction,     verse  section  of  the  human  me- 

ci        .  •  ,-\  i,,i  in  111  dulla  through  the  upper   part  of 

Sections  through  the  medulla  at  the    the  olives  bringing  the  giosso- 

/,     ,,  ,.  IT-  z'jx  pharyngeal    tract    (9.)    and   the 

upper  part  of  the  olivary  bodies  diner    lower  part  of  the  acoustic  nucleus 

-i-i        .  •  T-»  (80  into  view. 

little  from  the  former  sections.     But  a 

small  segment  of  the  olivary  bodies  is  present,  and  only  a  few 
of  the  hypoglossal  roots  remain.  (See  Fig.  139.)  External  to  the 
remains  of  the  hypoglossal  nucleus  is  a  nucleus  of  small  cells 


THE    OLIVARY    BODY. 


313 


giving  origin  to  a  bundle  of  fibres,  which  pass  out  laterally  just 
as  does  the  pneumogastric  lower  down.  This  is  the  glosso- 
pharyngeal  nerve  and  root.  Farther  still  from  the  median 
line,  in  the  floor  of  the  fourth  ventricle,  is  seen  a  group  of 
small  cells,  the  commencement  of  the  acoustic  nucleus.  Scat- 
tered nerve-cells  arising  here  pursue  an  obliquely  forward  and 
outward  direction,  making  the  lower  margin  of  the  auditory 
root. 

Transverse  sections  of  the  medulla  just  at  the  edge  of  the 
pons  bring  the  acoustic  region  into  view ;  the  upper  olivary 
body  is  here  visible.  Behind  this  are  scattered  a  few  large  cells, 
from  which  fibres  pass  backward  to  form  higher  the  facial  root. 


FIG.  140.— One-half  transverse  section  of 
the  human  medulla  just  below  the  edge  of  the 
pons,  showing  acoustic  nucleus  and  roots  which 
enclose  the  inferior  cerebellar  peduncle  I.  0. 
P. :  I,  internal  root ;  E,  external  root ;  v,  up- 
per olivary  nucleus ;  Lf ,  lower  facial  nucleus. 
3  diams. 


Fio.  141. — Diagram  of  a  transverse 
section  just  above  the  edge  of  the  pons, 
having  the  obliquity  given  it  in  Fig.  132, 
6  &  7 :  6,  abducens  root ;  7,  facial  root. 
For  other  explanations,  see  text. 


Occupying  the  floor  of  the  fourth  ventricle  is  a  large  mass  of 
gray  matter,  from  which  the  acoustic  arises.  This  gray  matter 
contains  many  small  round  and  some  multipolar  cells.  The 
nerve  has  two  roots,  one  internal,  the  other  external.  (See 
Fig.  140.)  The  former  arises  from  fibres  emerging  from  the 
raphe  near  the  fourth  ventricle  and  from  the  gray  matter  just 
external  to  it,  and  pursues  a  course  downward  and  forward 
through  the  lateral  white  matter.  This  root,  at  its  point  of 
emergence,  is  joined  by  fibres  from  the  posterior  root  curving 
i  around  the  surface  of  the  medulla,  like,  if  not  identical  with, 
the  arciform  fibres.  The  external  root  has  also  one  origin  from 
the  gray  matter  near  the  median  line,  and  curving  outward  on 


314  MANUAL   OF   HISTOLOGY. 

the  floor  of  the  fourth  ventricle  (forming  the  linece  transversce) 
it  receives  additions  from  the  lateral  gray  mass,  and  emerges 
from  the  medulla  a  little  behind  the  internal  root,  which,  how- 
ever, it  soon  joins. 

It  is  seen  that  the  two  roots  embrace  a  column  of  white 
matter,  which  is  the  inferior  peduncle  of  the  cerebellum.  (See 
Fig.  140.)  In  sections  just  above  the  edge  of  the  pons,  having 
the  oblique  direction  given  in  Fig.  132,  the  region  of  the  sixth 
and  seventh  nerves  comes  into  view.  The  view  presented  here 
is  different  from  that  in  the  medulla  below.  In  place  of  the 
narrow  band  of  arciform  fibres  which  covered  the  anterior  re- 
gion of  the  medulla,  nearly  the  anterior  half  of  this  section  is 
composed  of  transverse,  arciform  fibres.  Imbedded  in  this 
structure  is  a  longitudinal  bundle  of  white  matter,  the  contin- 
uation of  the  anterior  pyramid.  The  posterior  half  of  the 
section  contains  the  structures  under  consideration. 

From  a  group  of  multipolar  cells  at  the  floor  of  the  fourth 
ventricle,  some  distance  from  the  median  line,  several  bands  of 
fibres  pass  forward  and"  slightly  outward,  in  a  somewhat  sim- 
ilar way  to  the  hypbglossal  roots  lower  down.  This  is  the 
nucleus  and  root  of  the  abducens  nerve. 

Internal  to  and  .behind  the  abducens  nucleus,  in  almost 
all  sections,  is  seen  an  oval  bundle  of  what  at  first  sight  ap- 
pears to  be  longitudinal  nerve- 
fibres.  Closer  examination,  how- 
ever, shows  the  fibres  to  be  not 
straight  but  looped,  and  in  suc- 
cessful sections  the  following  ap- 
pearances are  presented.  Behind 
the  anterior  pyramids  and  out- 
side  of  the  abducens  root  is  seen 
a  group  of  multipolar  cells  oc- 

Fio.  142. — Diagram  of  course  of  fibres  in  r  •*• 

the  "  genn  "  of  the  root  of  the  facial  nerve  :  n  CUDying  tile  Same  lOCatlOU  aS  tll6 
fibres  coming  from  the  nucleus ;  g,  the  "  genu,'  *» 

or  coil  where  the  fibres  change  their  direction  grOUp  Called  tll6  lOW6r  facial  HU- 
B,  the  root  proper  of  the  facial  nerve. 

cleus,  lower  down.     Arising  from 

this,  and  pursuing  a  course  backward  and  inward,  are  numer- 
ous fibres  ;  these  reach  the  oval  bundle  before  mentioned,  enter 
it,  curl  upon  themselves  (see  Fig.  142),  and  emerge  at  about 
their  point  of  entrance.  The  fibres  mentioned  as  appearing 
longitudinal  undoubtedly  come  from  the  lower  facial  nucleus, 
and  curl  upon  themselves  like  the  rest. 


THE    OLIVARY    BODY.  315 

Some  fibres  (commissural)  join  the  root  from  the  raphe,  and 
others  seem  to  arise  from  the  abducens  nucleus,  though  this  is 
denied  by  many  authors.  The  fibres  which  seem  to  arise  from 
the  abducens  nucleus  are  probably  fibres  from  the  anterior 
nucleus  of  the  facial,  which  do  not  traverse  the  coil  ("genu," 
as  it  is  called),  but  enter  the  root  directly. 

The  facial  root  thus  formed  goes  directly  outward  at  first 
toward  the  external -angle  of  the  fourth  ventricle,  then  turns 
sharply  forward  to  emerge  at  the  junction  of  the  pons  and 
medulla  external  to  the  sixth  root.  Many  authors,  first  of 
whom  was  Clarke,  describe  an  inferior  nucleus  of  the  facial 
nerve,  supposing  it  to  innervate  the  lips  and  mouth,  basing 
their  assertions  as  much  on  the  seat  of  lesion  in  labio-glosso- 
pharyngeal  paralysis  as  on  anatomical  evidence.  There  can 
be  but  little  doubt  as  to  its  existence,  and  probably  it  corre- 
sponds to  the  group  of  cells  seen  in  Figs.  137  and  138. 

Sections  of  the  pons  above  this  point  soon  begin  to  show 
traces  of  the  fifth  nerve.  (See 
Fig.  143.)  The  picture  we  get 
in  transverse  sections  at  the 
emergence  of  the  fifth  root  is, 
in  front,  two  large  bundles  of 
longitudinal  nerve-fibres  sur- 
rounded by  the  arciform  fibres 
and  separated  by  the  raphe ; 
behind,  the  gray  matter  of  the 
fourth  ventricle,  which  here  is 
pentagonal  in  shape  and  is 

COVered    in     by    the    base    Of    the        ,J[IS-  143.-Diagram  showing  origin  and  course 
•  of  the  trigeinmus  nerve. 

cerebellum,  the  inferior  vermi- 
form process.  Emerging  from  the  gray  matter  in  front  of  the 
external  corner  of  the  ventricle,  and  also  joined  by  fibres  from 
above  and  below,  is  a  large  bundle  of  fibres  which  pursue  a 
diagonal  course  outward  and  forward,  to  emerge  from  the  side 
of  the  pons.  This  is  the  sensory  root  of  the  fifth  nerve.  Inter- 
nal to  this  root,  just  after  its  formation,  is  seen  in  successful 
sections  a  large  group  of  multipolar  cells  sending  off  fibres,  the 
motor  root,  which  join  the  sensory  root  and  emerge  with  it.  A 
collection  of  large,  oval,  pigmented  cells  here  underlie  the  exte- 
rior part  of  the  fourth  ventricle  and  form  the  locus  cceruleus. 
It  seems  to  have  an  indistinct  connection  with  the  trigeminal 


316 


MANUAL    OF    HISTOLOGY. 


FIG.  144. —Diagram  showing  ori- 
gin of  the  third  and  fourth  nerves 
from  the  gray  matter  about  the  aque- 
duct of  Sylvius :  c.  c.,  crus  cerebri ; 
3,  third  nerve ;  4,  fourth  nerve. 


sensory  root,  and  Meynert  makes  it  one  of   its    points  of 
origin. 

The  sensory  root  is  reinforced  by  fibres  from  a  group  of 
large  oval  cells  external  to  the  fourth  ventricle  and  by  the  so- 
called  descending  branch  (Meynert),  which  is  seen  in  trans- 
verse section  in  the  same  location  com- 
ing from  regions  still  higher  up.  Some 
fibres  also  come  from  the  raphe  and 
arcuate  fibres,  and  others  from  the  low- 
er sensory  origin  of  the  fifth,  which 
occupies  a  lateral  position  in  all  the 
sections  up  from  the  spinal  accessory 
region  of  the  medulla. 

V  ?<?  ^^     ^KUJ     J  Higher  in  the  pons.  where  the  ante- 

v_JS>  s%C5x  rior  motor  tracts  or  pyramids,  before 
mentioned,  begin  to  separate  into  the 
crura  cerebri,  the  fourth  nerves  are 
seen.  They  are  supposed  to  arise  from 
a  nucleus  at  the  floor  of  the  fourth  ven- 
tricle lower  down,  curve  around  the  outer  wall  of  the  ventricle, 
decussate  in  the  median  line  in  the  valve  of  Yieussens,  and 
pass  from  the  pons  behind  the  tubercula  quadrigemina.  From 
this  point  they  curve  forward  around  the  crura,  on  the  outer 
side  of  which  they  appear  at  the  base  of  the  brain. 

At  about  this  point  and  a  little  higher  are  seen  bundles  of 
fibres  emerging  from  the  gray  matter  containing  small  cells, 
in  front  of  the  fourth  ventricle,  diverging  and  pursuing  an 
arcuate  course  through  the  crura,  to  converge  again  and  emerge 
from  the  inner  side  of  each  crus.  (See  Fig.  144.)  This  consti- 
tutes the  nucleus  of  origin,  the  course  and  point  of  emergence 
of  the  third  nerve — a  view  hard  to  get  unless  just  the  right 
obliquity  is  given  to  the  section. 

Imbedded  in  the  crus,  in  the  region  through  which  the  third 
nerve  passes,  is  a  collection  of  pigmented  cells  forming  the  locus 
niger.  Higher  the  crura  separate  and  enter  their  respective 
hemispheres.  Their  further  course  is  better  shown  by  a  trans- 
verse vertical  section  of  the  hemispheres  at  the  large  part  of 
the  thalamus  opticus.  (See  Fig.  145.) 

Here  we  see  a  great  part  of  the  substance  of  the  crus  flat- 
tened in  form  passing  upward,  between  the  optic  thalamus  and 
a  gray  mass  called  the  nucleus  lenticularis,  forming  what  is 


THE    CEREBELLUM.  317 

denominated  the  internal  capsule.  The  posterior  third  of  the 
internal  capsule  is  distributed  to  the  posterior  part  of  the 
hemisphere,  and  when  destroyed  produces  loss  of  sensibility 
on  the  opposite  side  of  the  body.  The  anterior  two-thirds  of 
the  internal  capsule  is  distributed  to  the  middle  or  motor  re- 
gion of  the  hemisphere,  and  its  destruction  causes  a  paralysis 


N  C      M  R  o 


EC  ML 


FIG.  145.— Modified  from  Charcot's  diagram  to  show  position,  relation,  and  distribution  of  the  inter- 
nal capsule  as  seen  in  a  vertical  transverse  section  of  the  brain  on  a  level  with  the  greatest  development 
of  TO,  thalamus  opticus  ;  1C,  location  of  the  internal  capsule  :  NL,  nucleus  lenticularis  ;  EC,  external 
capsule ;  D,  claustrum ;  NC ;  nucleus  caudatus ;  MRC,  motor  regions  of  cortex  cerebri ;  1,  fibres  repre- 
senting the  radiation  of  the  internal  capsule  vertically  to  the  motor  region  of  the  cortex. — From  "Lec- 
tures on  Localization,"  by  Dr.  E.  C.  Seguin  :  New  York  Medical  Hecord,  p.  142,  August  24, 1878. 

of  the  opposite  side  of  the  body.  The  fibres  expanding  from 
the  internal  capsule,  joined  by  those  emanating  from  the  gan- 
glia at  the  base  and  the  corpus  callosum,  form  a  fan-shaped 
expansion  of  white  fibres  called  the  corona  radiata. 


THE   CEREBELLUM. 

The  white  centre  of  the  cerebellum,  formed  from  the  ex- 
pansion of  the  peduncular  tracts,  incloses  a  collection  of  gray 
substance,  the  corpus  dentatum.  This  body,  visible  in  all 
sections,  bears  some  resemblance  to  the  olivary  body  in  the 
medulla,  on  account  of  its  irregular,  dentated  outline.  Its 
greater  consistence  causes  it  to  stand  out  in  a  section  from  the 
surrounding  tissue.  In  intimate  structure  this  body  consists 


318 


MANUAL    OF    HISTOLOGY. 


of  a  collection  of  small  fusiform  and  polyhedral  cells  with 
minute  processes,  imbedded  in  a  basis-substance  much  more 
dense  than  the  surrounding  white  matter.  The  body  is  made 
to  appear  striated  in  a  peripheral  direction  by  bundles  of 
fibres  and  blood-vessels  pursuing  a  parallel  course. 

The  surface  of  the  cerebellum,  deeply  gashed  by  sulci  and 
their  subdivisions,  presents,  on  section,  its  well-known  com- 
pound, arborescent  appearance.  This  arrangement  of  the  gray 
matter  causes  the  greatest  possible  surface  to  come  in  con- 
tact with  the  blood-current  furnished  by  the  pia  mater,  and 
hence  secures  the  greatest  nutrition  of  the  elements  of  the 
cortex.  The  gray  matter  of  the  cortex  is  easily  divisible  into 
an  external  or  granular  layer,  a  middle  or  cellular  layer,  and 
an  internal  or  nuclear  layer.  The  latter  consists  of  a  vast 
number  of  small  granular  cells  about  the  size  of  white  blood- 
corpuscles,  which  take  staining  fluids  with  great  avidity.  The 
middle  stratum  is  a  clear  space  in  which  there  is  a  single  layer 
of  large  corpuscles,  called  the  cells  of  Purkinje,  10  to  40  p.  in 

diameter.  They 
are  scattered  at 
some  distance 
from  each  other, 
and  present  pe- 
culiarities pos- 
sessed by  no  other 
cells  in  the  body. 
The  cells  are  of 
large  size,  vary- 
ing in  form  from 
fusiform  to  flask- 

'146'~Diagram  o£  the  cerebeUar  ""^  showins  the  krge  ceUs  of  shaped,      accord- 

ing  to  the  plane  of 
the  section.  Their  central  side  is  round,  and  in  most  cases  has 
no  processes.  Often  the  usual  rounded  contour  of  the  cell- 
body  is  broken  by  an  angle,  seemingly  the  remains  of  a  broken 
process.  Here  and  there  a  large  non-branching  axis-cylinder 
process  is  seen  emerging  from  the  base  of  a  cell  and  pursuing 
a  course  parallel  to  the  cortex.  That  these  basal  processes 
exist  in  all  cases,  and  ultimately  acquire  a  myelinic  sheath, 
there  is  no  doubt.  (See  Fig.  146.) 

From  the  peripheral  side  large  arborescent  processes  spring, 


pun'e 


THE    CEREBRAL    GANGLIA.  319 

which  pursue  quite  a  direct  course  through  the  external  or 
granular  layer  and  disappear  when  near  the  periphery.  The 
primary  processes,  one  or  two  in  number,  have  a  tendency  to 
spring  from  the  cell-body  at  an  obtuse  angle,  and  give  off  at 
almost  right  angles  to  themselves  the  straight  peripheral  pro- 
cesses already  mentioned.  The  nuclei  of  these  cells  are  oval 
and  coarsely  granular ;  the  nucleolus  is  round  and  small. 

TJie  cortex  proper  consists  of  a  granular  matrix  vertically 
striated  by  the  cell-processes  and  parallel  blood-vessels.  There 
is  also  a  moderate  sprinkling  of  small  round  cells  and  nuclei 
similar  to  those  in  the  third  layer.  The  cortex  is  very  vascular. 

THE   CEREBRAL   GANGLIA. 

As  examples  of  these  structures  the  optic  thalami  and  cor- 
pora striata  may  be  taken. .  They  are  collections  of  gray  matter 
through  which  part  of  the  fibres,  emanating  from  the  crura  to 
help  form  the  corona  radiata,  pass. 

In  the  corpus  striatum  these  fibres  pass  through  in  bundles 
visible  to  the  naked  eye,  which  gives  to  this  body  its  striated 
appearance.  These  bundles  radiate  toward  the  periphery  of 
the  body,  thus  leaving  ever  increasing  spaces  between  them. 
These  spaces  at  the  base  of  the  body,  at  the  point  of  entrance 
of  the  bundles  from  the  crura,  are  narrow,  filled  with  nerve- 
fibres  running  in  horizontal,  vertical,  and  diagonal  directions, 
seemingly  commissUral  in  nature,  and  multipolar  cells  few  in 
number,  large,  and  resembling  somewhat  cells  of  the  anterior 
horns  of  the  spinal  cord,  whose  processes  mingle  with  the  fibres 
mentioned.  Nearer  the  periphery  of  the  organ,  where  the  bun- 
dles of  fibres  are  more  widely  separated,  the  intervening  mass  of 
fibres  and  cells  abruptly  changes  to  a  finely  granular  gray  ma- 
trix, holding  in  its  substance  numerous  small  blood-vessels 
and  small  nerve-cells,  mostly  round — some,  however,  triangular 
in  shape,  similar  to  those  of  the  second  layer  of  the  cere- 
bral cortex.  They  have  large  nuclei  and  many  delicate  pro- 
cesses. 

The  optic  thalami  consist  of  a  mixture  of  gray  matter  and 
fibres,  not,  however,  so  regularly  arranged  as  in  the  corpus 
striatum.  The  gray  matter  contains  a  few  oval  cells  having 
many  delicate  processes. 

The  cerebral  ventricles. — Continuous  with  the  central  canal 


320 


MANUAL    OF    HISTOLOGY. 


FIG.  147.— Diagram  illustrating  the 
structure  of  the  ependyma  of  the  cere- 
bral ventricles. 


of  the  cord,  and  doubtless  like  it  in  function,  the  cerebral  ven- 
tricles resemble  it  in  their  structure.  They  are  lined  through- 
out with  a  structure  called  the  ependyma.  This  consists  first 
of  a  finely  granular  layer  covering  all  the  nervous  matter 
bounding  the  ventricles.  Besides  the  minute  granules,  this 

layer  contains  a  few  small  nuclei  here 
and  there,  but  no  fibres.  On  its  free 
surface  rests  a  single  layer  of  cylin- 
drical epithelium.  The  cells  of  this 
layer  have  square  free  ends,  while 
they  are  anchored  by  one  or  more 
delicate  processes  which  emerge  from 
the  attached  end  and  pierce  the  sub- 
jacent granular-matrix.  These  epi- 
thelia  in  the  fresh  state  undoubtedly  have  cilia.  This  layer 
of  epithelium  is  apt  to  be  arranged  in  folds,  giving  a  section 
of  the  ependyma  a  wavy  appearance. 

The  choroid  plexus  of  the  lateral  ventricles  has  for  its  basis 
an  artery  which  enters  the  descending  horn  of  the  lateral  ven- 
tricle from  the  base  of  the  brain.  This  artery  gives  off  along 
its  course  short  arterial  trunks  which  repeatedly  subdivide,  and 
each  ultimate  arteriole  terminates  in  a  convoluted  capillary 
loop,  resembling  the  Malpighian  tuft  of  the  kidney.  Some 
of  the  twigs  seem  to  end  in  a  cse- 
cal  extremity ;  but  it  is  doubtful 
wheth&r  they  do,  the  preparations 
giving  this  appearance  being  prob- 
ably artificial.  The  peculiarity  of 
the  choroid  plexus  is  that  all  the 
vessels  composing  it,  large  and 
small,  are  covered  by  a  layer  of 
polyhedral  epithelial  cells,  each 
having  one,  sometimes  two  large 
nuclei.  This  presents  a  beautiful 
example  of  the  so-called  tesselated 
epithelium,  each  cell  being  sepa- 
rated from  its  neighbor  by  a  transparent  intercellular  sub- 
stance. This  epithelial  covering  causes  the  tufts  of  the  choroid 
plexus  to  resemble,  in  a  degree,  the  villi  of  the  chorion.  The 
best  plan  in  studying  the  choroid  plexus  is  to  use  hsema- 
toxylon,  or  alcoholic  specimens  slightly  teased. 


FIG.  148.— Diagram  showing  structure 
of  the  choroid  plexus  of  the  lateral  ven- 
tricles. 


THE    CEREBRAL    GANGLIA.  321 

The  cerebral  dura  mater  differs  from  the  spinal  in  the  fact 
that,  its  outer  surface  serving  as  periosteum,  it  lacks  the  layer 
of  loose  connective  tissue  present  in  the  spinal  dura  mater. 
Its  bulk  consists  of  two  layers  of  dense  fibrous  tissue  running 
in  opposite  directions.  The  inner  serous  surface  is  coated  with 
endothelium  and  lymphatics.  The  outer  or  periosteal  surface 
is  the  most  vascular.  The  cerebral  differs  from  the  spinal  arach- 
noid only  in  being  perhaps  a  little  more  closely  attached  to 
the  pia  mater.  The  pia  mater  of  the  brain  is  extremely  vascu- 
lar, and  shows  more  beautifully  than  the  spinal  membrane  the 
system  of  perivascular  spaces. 

The  cerebral  cortex. — The  cerebral  cortex  is  a  thin  sheet  of 
gray  matter  spread  on  the  outer  surface  of  the  hemispheres. 
The  outer  surface  of  the  hemispheres  is  grooved  by  furrows 
(sulci)  less  deep  in  proportion  to  their  size,  and  less  regular 
than  those  of  the  cerebellum.  The  convolutions  produced  by 
these  sulci,  although  seemingly  very  irregular,  still  have  a  cer- 
tain symmetry  in  different  brains  by  which  they  can  be  classi- 
fied and  named.  A  definite  knowledge  of  these  facts  is  neces- 
sary for  an  understanding  of  the  current  literature  on  the 
subject  and  of  properly  recording  cases. 

The  fetal  hemisphere  at  an  early  date  is  smooth.  Furrows 
soon  begin  to  appear,  the  first  and  most  important  of  which  is 
the  fissure  of  Sylvius,  extending  upward  and  backward,  from 
about  the  anterior  third  of  the  base  of  the  brain,  and  the  fis- 
sure of  Rolando,  running  from  near  the  posterior  extremity  of 
the  fissure  of  Sylvius  upward  to  the  superior  longitudinal  fis- 
sure. One  after  another  the  other  fissures  appear,  till  in  the 
adult  brain  they  seem  innumerable.  Even  here,  however,  there 
is  a  certain  constant  arrangement  of  fissures  and  convolutions 
on  which  a  nomenclature  may  be  based. 

The  original  fissures  of  Sylvius  and  Rolan do  remain.  From 
the  anterior  inferior  part  of  the  frontal  lobe  three  furrows  run 
obliquely  upward  and  backward  toward  the  two  fissures  just 
named,  dividing  the  frontal  region  into  the  three  frontal  con- 
volutions, while  a  convolution  in  front  of  the  fissure  of  Rolando 
receives  the  name  of  the  ascending  frontal  or  anterior  central 
convolution.  A  similar  convolution  behind  the  fissure  is  called 
the  ascending  parietal  or  posterior  central  convolution.  The 
parietal  region  is  irregularly  divided  from  above  downward, 
as  is  also  the  temporo-sphenoidal  and  occipital  region.  The 

21 


322 


MANUAL    OF   HISTOLOGY. 


base  of  the  brain  is  also  divided  into  a  series  of  basal  frontal, 
temporal  and  occipital  convolutions.  By  far  the  most  impor- 
tant region  of  the  cortex,  according  to  our  present  knowledge, 
is  that  along  the  fissures  of  Sylvius  and  Rolando,  the  so-called 
motor  tract  of  the  TiemispJieres.  The  exact  physiological  func- 
tions of  the  anterior  frontal,  the  occipital,  temporal,  and  basal 


FIG.  149. — Modified  from  Ferrier ;  letters  and  figures  the  same :  8,  fissure  of  Sylvius ;  c,  fissure  of 
"Ronaldo :  po,  parieto-occipital  fissure ;  A,  ascending  frontal  gyrus ;  B,  ascending  parietal  gyrus ;  F2, 
.third  frontal  gyrus ;  Pa',  gyrna  angularis  ;  circle  I.,  seat  of  lesions  which  (on  the  left)  cause  aphasia; 
'circle  II.,  seat  of  lesions  which  convulse  or  paralyze  the  upper  extremity  of  the  opposite  side;  dotted 
circle  III.,  seat  of  lesions  which  probably  convulse  or  paralyze  the  face  on  the  opposite  side ;  dotted  oval 
IV.,  seat  of  lesions  which  probably  convulse  or  paralyze  the  lower  extremity  of  the  opposite  side.  These 
•districts  receive  their  blood-supply  chiefly  from  the  middle  cerebral  artery. — From  Lectures  on  Localiza- 
tion by  Dr.  B.  C.  Seguin :  N.  Y.  Medical  Record,  October  19, 1878,  p.  301. 

regions  of  the  hemispheres,  is  not  known,  inference,  however, 
making  them  the  seat  of  general  and  special  sense,  vaso-motor, 
psychic  centres,  etc.,  etc. 

The  middle  or  f  ronto-parietal  region,  however,  is  the  proven 
seat  of  motor  centres  for  the  face,  limbs,  and  body,  and  the 
faculty  of  articulate  language.  The  centre  for  speech  occu- 
pies the  region  at  the  base  of  the  third  frontal  convolution 
and  the  island  of  Reil  on  the  left  side,  a  similar  location  on 
the  right  side  being  occupied  by  a  centre  for  articulatory 
movements.  A  little  higher  on  the  ascending  frontal  and 
parietal  convolutions  is  an  area  having  control  over  the  move- 
ments of  the  tongue  and  face.  Still  higher  is  found  a  larger 
space,  the  centre  for  the  arm  of  the  opposite  side.  A  larger 
space  at  the  junction  of  the  fissure  of  Rolando  and  the  su- 


THE  CEREBRAL  GANGLIA. 


323 


perior  longitudinal  fissure,  including  a  tract  on  the  inner 
aspect  of  the  hemisphere,  called  the  paracentral  lobule,  is  the 
centre  for  movements  of  both  extremities,  especially  the  lower. 
On  account  of  the  anatomical  variability  of  the  convolutions 
in  different  brains,  these  centres  must  be  allowed  some  lati- 
tude, and  should  not  be  made  so  small  and  exactly  located 
as  they  are  by  some  authors.  Their  location  has  been  pretty 
definitely  determined,  however,  by  experimentation  on  animals, 
and  lesions  in  man,  such  as  trauma- 
tisms,  neoplasms,  abscesses,  hemor- 
rhages, atrophy  following  amputa- 
tions, retarded  development,  etc. 

Possessing  such  important  proper- 
ties we  should  naturally  expect  the 
cerebral  cortex  to  be  a  very  complex 
structure,  and  so  it  is. 

Minute  structure  of  the  cortex. — 
In  order  to  get  a  satisfactory  view  of 
the  elements  of  the  cortex,  great  care 
has  to  be  exercised  in  making  sections. 
It  is  not  enough  to  make  a  section 
exactly  perpendicular  to  the  cortex. 
The  plane  of  the  section  must  exactly 
coincide  with  the  direction  of  the  fibres 
of  the  corona  radiata  as  they  enter  the 
convolution.  This  can  be  rather  easily 
accomplished  by  paying  close  atten- 
tion to  the  arrangement  of  the  white 
and  gray  matter  in  the  piece  from  which  the  sections  are  to 
be  made.  Cuts  with  any  obliquity  will  give  erroneous  impres- 
sions as  to  the  exact  shape  and  structure,  especially  of  the 
cellular  elements  of  the  cortex.  The  cortex  cerebri  is  generally 
divided  into  five  layers,  but  it  is  easily  divisible  into  three  only. 

The  outer  layer,  lying  immediately  under  the  pia  mater,  is 
more  transparent  than  the  rest,  and  is  composed  of  a  fine  net- 
work of  neuroglia  containing  many  quite  large  openings,  giving 
it  a  spongy  appea,rance.  It  also  contains  a  few  large,  round 
nuclei,  and  a  small  number  of  triangular  nerve-cells. 

The  second  layer,  thicker  than  the  first,  consists  of  a  gray 
basis-substance,  dense  and  granular,  holding  an  immense  num- 
ber of  small,  triangular  and  conical  cells,  their  apex  being  di- 


FIG.  150.— Diagram  showing  the 
elements  and  relation  of  parts  in  the 
cerebral  cortex.  (See  text.) 


324  MANUAL    OF    HISTOLOGY. 

rected  toward  the  periphery  and  often  drawn  out  into  a  slen- 
der axis-cylinder  process,  while  from  their  base  several  delicate 
processes  are  given  off.  These  cells  all  have  large  nuclei  and 
nucleoli.  Here  and  there  are  seen  larger  conical  cells,  which 
will  be  described  with  the  next  layer.  The  characteristic  fea- 
ture of  the  second  layer,  however,  is  the  presence  of  a  great 
number  of  small,  round  cells  and  free  nuclei  similar  to  those  in 
the  third  layer  of  the  cerebellar  cortex. 

In  the  third  layer  the  matrix  is  still  more  dense,  and  con- 
tains, besides  a  few  small  triangular  cells,  round  cells,  and  free 
nuclei,  a  large  number  of  large  conical  corpuscles,  the  so-called 
u giant  cells"  of  the  cortex,  the  distinguishing  feature  of  this 
layer.  When  isolated  from  their  surroundings  these  cells  ap- 
pear like  cones  which  taper  gradually  from  a  broad  base  to  a 
very  slender  apex,  which,  when  it  attains  the  size  of  an  axis- 
cylinder,  can  be  traced  for  a  long  distance  without  showing  a 
division.  This  undoubtedly  terminates  in  a  myelinic  nerve- 
fibre.  The  base  of  the  cell  is  not  square,  but  crenated  and 
notched  by  the  giving  off  of  numerous  delicate  basal  processes 
which  are  lost  in  the  granular  matrix. 

The  cells  all  have  nuclei  and  nucleoli,  most  of  which  are 
round,  but  some  of  which  seem  also  to  have  a  triangular  shape 
corresponding  to  the  cell-body.  The  cells  average  25  /*.  in 
diameter.  A  great  difference  is  made  in  the  apparent  shape  of 
the  cell  by  obliquity  of  the  section.  If  the  line  of  section  is 
moderately  oblique,  it  shortens  the  cells  ;  if  still  more  oblique, 
it  makes  them  very  short  and  blunt ;  while  if  the  section  is  at 
right  angles  to  their  axis,  all  the  cells  appear  round  and  of 
various  sizes.  In  the  deepest  parts  of  this  layer  the  giant-cells 
gradually  disappear,  and  the  gray  matter  of  the  cortex  merges 
into  the  white  matter.  In  the  two  inner  layers  of  the  cortex 
there  are  seen  many  fibres  and  bundles  of  fibres  having  a  ver- 
tical direction,  which,  with  the  blood-vessels  (the  largest  of 
which  being  perpendicular  to  the  surface),  give  the  cortex  a 
somewhat  striated  appearance. 

We  see,  then,  that  the  only  difference  between  the  second 
and  third  layers  of  the  cortex  is  the  greater  number  of  small 
cells  in  the  second  and  the  greater  number  of  large  cells  in  the 
third,  while  the  division  of  the  third  layer  into  three,  as  is 
accepted  by  most  authors,  seems  purely  arbitrary,  there  being 
a  gradual  gradation  into  the  white  substance. 


BIBLIOGRAPHY.  325 

Some  writers l  lay  much,  stress  on  the  difference  of  structure 
of  the  cortex  in  different  regions  of  the  hemisphere.  It  is  true 
that,  in  the  non-excitable  or  sensory  regions,  the  cortex  is  thin- 
ner and  perhaps  less  highly  organized ;  but  here  are  met  the 
same  elements  as  form  the  cortex  in  the  motor  region  (centre, 
for  the  arm,  for  instance).  (See  Fig.  150.)  Even  the  giant-cells 
are  found  less  numerously  than  in  the  motor  regions.  Another 
fact  demands  attention,  that  is,  that  the  structure  of  the  cortex 
is  the  same  at  the  bottom  of  a  fissure  as  on  the  surface  of  a 
convolution,  and  for  this  reason  lesions  of  the  sides  and  bottom 
of  fissures  should  receive  as  much  attention  as  those  of  the 
surface  of  the  convolutions,  implicating,  as  they  do,  equally  im- 
portant structures. 


BIBLIOGRAPHY. 

SPINAL  CORD. 

CLARKE,   J.   L.     Researches  into  the   Structure  of  the  Spinal  Cord.     Philosoph. 

Transactions.     1850. 
BONDERS,  F.  C.     Dissertatio  anatomica  inauguralis  de  cerebri  et  medullae  spinalis 

systeraata  vasorum  capillari  in  statu  sano  et  morboso.     1853. 
JACUBOWITSCH,  N.    Mittheilungen  iiber  die  f  einere  Structur  des  Gehirns  und  Riicken- 

marks.     Breslau,  1857. 

JACUBOWITSCH,  N.     Further  Researches  into,  etc.     Breslau,  1858. 
BIDDER,  F.,  und  KUPFFER,  C.     Untersuchungen  iiber  die  Textur  des  Riickenmarks, 

etc.     Leipzig,  1859. 
VAN  DER  KOLK,  SCHROEDER.     Minute  Structure  and  Functions  of  the  Spinal  Cord 

and  Medulla  Oblongata,  and  on  the  Proximate  Cause  and  Rational  Treatment 

of  Epilepsy.     New  Sydenham  Society.     London,  1859. 
STILLING,  B.     Neue  Untersuchungen  iieber  den  Bau  des  Ruckenmarks.     Cassel, 

1859. 
LUYS,  J.     Recherches  sur  le  systeme  nerveux  cerebro-spinal ;  sa  structure,  sea  fonc- 

tions  et  ses  maladies.     Paris,  1865. 
His,  W.     Zum  Lymphsystem.     Leipzig,  1865. 
HIRSCHFELD,  LuDOVic.     Traite  et  iconographie  du  systeme  nerveux  et  des  organes 

des  sens  de  1'homme.     Paris,  1866. 

JOLLY,  F.     Ueber  die  Ganglienzellen  des  Ruckenmarks.     Miinchen,  1866. 
KOLLIKER,   A.     i&lements    d'histologie   humaine.     Traduit  par  Marc  See.     Paris, 

1868. 

1  See  Betz :  Anatomischer  Nachweis  zweier  Gehirncentra.  Centralblatt  f  iir  die 
Medicinischen  Wissenschaften,  August  1  and  8,  1874,  pp.  578  and  595.  He  finds 
"  nests  "  of  enormous  cells  in  the  motor  area,  especially  of  the  paracentral  lobule. 


326  MANUAL    OF    HISTOLOGY. 

HENLE,  J.     Handbuch  der  Nervenlehre  des  menschen.     Braunschweig,  1871. 

GEULACII,  J.  The  Spinal  Cord.  Translated  by  Dr.  E.  C.  Seguin,  in  Strieker's  His- 
tology. 1872. 

ScnULTZE,  MAX.  The  General  Character  of  the  Structures  Composing  the  Nervous 
Substance.  Translated  by  Henry  Power.  Strieker's  Histology.  1872. 

RETZIUS,  GUST,  och  KEY,  AXEL.  Studier  i  nervsystemets  anatomi.  Stockholm, 
1872. 

ERB,  W.  H.  Diseases  of  the  Spinal  Cord  and  Medulla  Oblongata  (Anatomical  Intro- 
duction). Ziemssen's  Cyclopaedia  of  Medicine.  Vol.  XIII.  American  Edi- 
tion. 1878. 

SEGUIN,  E.  C.  Lectures  on  the  Localization  of  Spinal  and  Cerebral  Diseases.  N.  Y. 
Medical  Record.  1878. 

FORT,  J.  A.     Lemons  sur  les  centres  nerveux.     Paris,  1878. 

HUGUENIN,  G.  Anatomie  des  centres  nerveux.  Traduit  par  Dr.  Th.  Keller. 
Paris,  1879. 

BRAIN. 

BERLIN,  RUDOLF.     Beitrag  zur  Structurlehre  des  Grosshirnwindungen.     Erlangen, 

1858. 

KUPFFER,  GUST.     De  cornus  ammonis  textura.     Dorpat,  1859. 
CLARKE,  J.  L.     Researches  on  the  Intimate  Structure  of  the  Brain,  Human  and 

Comparative.     1857  and  1867. 

ARNDT,    RUDOLF.     Studien  iiber  die  Architektonik  der  Grosshirnrinde   des  Men- 
schen.    Bonn,  1867-68. 
JENSEN,  JULIUS.     Die  Furchen  und  Windungen  der  menschlichen  Grosshirn  Hemis- 

pharen.     Berlin,  1870. 
MEYNERT,  T.     The  Brain  of  Mammals.     Strieker's  Histology.     Am.  edition.     New 

York,  1872. 

HITZIG,  EDWARD.     Untersuchungen  iiber  das  Gehirn.     Berlin,  1874. 
CHARCOT,  J.  M.     Lejons  sur  les  localisations  dans  les  maladies  du  cerveau.     Paris, 

1876. 

BENEDIKT,  MORIZ.     Anatomische  Studien  an  Verbrecher-Gehirnen.     Wien,  1879. 
BOYER,  H.  DE.     Etudes  topographiques  sur  les  lesions  corticales  des  hemispheres 

cerebraux.     Paris,  1879. 

FERRIER,  DAVID.     The  Localization  of  Cerebral  Disease.     New  York,  1879. 
STRICKER  und  UNGER.     Untersuchungeu  iiber  den  Bau  der  Grosshirnrinde.    Wiener 

Anzeiger,  1879. 
BEVAN  LEWIS  and  CLARKE,  H.     The  Cortical  Lamination  of  the  Motor  Area  of 

the  Brain.     Proceedings  of  the  Royal  Society,  Vol.  XXVII.     1879. 


CEREBELLUM. 

HESS,  N.     De  cerebelli  glorum  textura.     Dorpat,  1858. 

SCHULTZE,  F.  E.     Ueber  den  feineren  Bau  der  Rinde  des  kleinen  Gehirnes.     Ros- 
tock, 1863. 

CENTRAL  NERVOUS  SYSTEM. 

DEITERS,  OTTO.     Untersuchungen  iiber  Gehirn  und  Riickenmark  des  Menschen  und 
der  Saugethiere.     Braunschweig,  1865. 


BIBLIOGRAPHY.  327 

DEECKE,  THEODOKE.  Perivascular  Spaces  in  the  Nervous  System.  American  Jour- 
nal of  Insanity.  January,  1874. 

WALDEYER.  Beitrage  zur  Kenntniss  der  Lymphbahnen  des  Centralnervensyst. 
Arch.  f.  mikr.  Anat.  1879. 

KESTEVEN,  W.  H.  The  Structure  and  Functions  of  the  Olivary  Bodies.  St.  Bar- 
tholomew's Hospital  Reports.  1879. 

SEE,  MARC.  Sur  la  communication  des  cavi'tes  ventriculaires  de  1'encephale  avec  lea 
espaces  sous-arachno'idiens.  Revue  mensuelle.  1879. 

BROCA,  P.     Localisations  cerebrales.     Revue  d'anthropol.     1879. 


CHAPTER  XX. 

THE  EYE. 
BY  C.  H.  WILLIAMS,  M.D.,  BOSTON,  MASS. 

THE  eyelids  are  very  complicated  structures.  Their  exter- 
nal coating  is  formed  of  skin,  which  is  modified  for  the  special 
purpose  it  has  to  serve  in  this  situation.  Beneath  the  skin  is  a 
loose  sheet  of  connective  tissue  ;  still  more  internally  is  the  lit- 
tle orbicular  is  palpebrarum  muscle  ;  behind  this  again  is  loose 
connective  tissue,  which  shades  off  gradually  into  the  tarsus. 
This  latter  is  not  formed  of  cartilage,  as  was  formerly  sup- 
posed, but  of  dense  fibrous  tissue.  The  conjunctiva  tarsi 
lines  the  inner  surface  of  the  tarsus.  The  skin  of  the  lids 
exhibits  the  usual  layers  of  horny,  serrated,  and  cylindrical 
epithelium.  At  the  upper  portions  the  papillae  are  sparsely 
developed  and  short,  but  they  gradually  increase  in  size  and 
number  as  they  approach  the  free  edges.  A  peculiarity  of  this 
skin  are  the  pigment-cells,  which  are  scattered  throughout  the 
cutis.  They  are  more  abundant  in  brunettes  than  in  blondes. 

At  the  confronting  margins  of  the  lids  are  found  the  cilia 
or  eyelashes,  which  resemble  the  ordinary  larger  hairs  in  their 
formation  and  mode  of  growth  ;  they  are  placed  in  two  or 
three  rows,  are  well  supplied  with  pigment,  and  have  a  definite 
direction  given  to  them  by  the  deep  follicles  from  which  they 
grow. 

Ordinary  sweat-glands  are  quite  numerous,  especially  in  the 
upper  portions  of  the  lid  ;  at  the  lower  border  we  occasionally 
find  them  in  a  modified  form,  opening  into  sebaceous  follicles 
near  or  just  behind  the  cilia ;  they  have  a  long  and  wide  ori- 
fice, and  the  tubules  are  filled  with  fine  granular  matter,  con- 
taining occasional  roundish  masses  resembling  particles  of 
albumen. 

Beneath  the  cutis  is  a  loose  connective-tissue  layer  through 


THE   EYE.  329 

which  numerous  blood-vessels  and  nerves  pass ;  behind  this, 
and  covering  the  whole  extent  of  the  lid,  are  bundles  of  the 
orbicularis  palpebrarum  ;  some  small  fasciculi  of  this  muscle 
are  also  found  at  the  lower  and  inner  angle  of  the  lid,  enclosing 
the  openings  of  the  Meibomian  glands.  These  bundles,  known 
as  the  musculus  ciliaris  Riolani,  have  fibres  which  are  among 
the  smallest  of  the  striped  variety  of  muscular  tissue. 

Behind  this  layer  is  a  thin  sheet  of  loose  connective  tissue, 
which  merges  without  any  sharp  boundary  line  into  the  tar- 
sus ;  this  latter  body  forms  a  leaf-shaped  plate  about  twenty 
millimetres  in  length  by  one  millimetre  in  thickness,  and  is 
composed  of  very  dense  connective-tissue  fibres  separated  only 
by  minute  lymph-spaces ;  it  has  few  blood-vessels  or  nerves, 
and  serves  to  give  the  requisite  stiffness  to  the  looser  tissues  of 
the  Ud. 

The  Meibomian  glands  are  imbedded  in  the  tarsus.  Their 
excretory  ducts,  which  are  directed  at  right  angles  to  the  pal- 
pebral  margin,  have  their  openings  on  the  surface  of  the  lid 
near  its  posterior  angle.  They  are  lined  with  epithelium,  which 
at  the  external  orifice  is  similar  to  that  in  the  superficial  parts 
of  the  skin  ;  more  internally  it  is  serrated,  while  in  the  acini  of 
the  gland  it  has  a  cuboidal  shape.  These  glands  have  a  straight 
central  tube,  around  which  the  acini  are  clustered,  and  into 
which  they  discharge  the  sebum,  a  material  composed  of  epi- 
thelial cells  that  have  undergone  fatty  degeneration.  This 
oleaginous  substance  serves  to  moisten  the  edges  of  the  lid  and 
to  prevent  the  overflow  of  tears. 

Above  the  Meibomian  glands,  and  in  part  imbedded  in  the 
tarsus,  are  the  acinous  glands,  which  have  their  openings  on 
the  surface  of  the  conjunctiva  fornicis.  Above  these  glands 
the  smooth  muscular  fibres  of  the  little  palpebralis  muscle  of 
Muller  are  inserted,  through  a  tendon,  into  the  upper  part  of 
the  tarsus ;  the  fibres  of  this  muscle  are  quite  large  and  have 
peculiar  irregular  cells  with  pigmented  nuclei  scattered 
throughout  them. 

To  prepare  sections  from  the  lids  they  should  be  pinned  fiat 
on  a  piece  of  cork  and  then  immersed  in  Muller' s  fluid'  for 
eight  days.  After  being  washed  in  water  they  are  placed  in 
absolute  alcohol  until  sufficiently  hard  ;  or  they  may  be  hard- 

1  See  chapter  on  General  Methods. 


330  MANUAL    OF   HISTOLOGY. 

ened  by  placing  in  the  ordinary  £  per  cent,  solution  of  chloride 
of  gold.  This  last  method  shows  very  clearly 'the  nerves  of 
the  lid  and  conjunctiva,  which  take  a  deep  violet  or  mauve 
color.  For  rapid  work  the  lids  may  be  hardened  in  a  saturated 
solution  of  picric  acid.  They  may  then  be  stained  with  picro- 
carmine  or  hsematoxylon,  and  mounted  in  glycerine  or  balsam. 
(See  chapter  on  General  Methods.) 

The  caruncula  lachrymalis  is  a  small,  rounded  mass  of 
skin ;  it  is  placed  between  the  lids  at  their  inner  angle,  and 
contains  hairs,  vessels,  and  glands,  such  as  are  found  else- 
where in  the  cutis.  Its  office  is  to  prevent  the  overflow  of  tears. 

The  conjunctiva. — Just  behind  the  tarsus,  and  separated 
from  it  by  a  thin  layer  of  fibrillated  connective  tissue,  is  the 
conjunctiva,  which,  after  lining  the  inner  surface  of  the  lid, 
passes  backward  as  a  loose  connecting  fold  (fornix)  to  the 
sclera,  over  which  it  is  reflected  forward  as  far  as  the  margin 
of  the  cornea.  The  conjunctiva  consists  of  an  external  or 
epithelial  layer  and  a  tunica  propria  or  proper  investing  mem- 
brane. There  is  also  a  subconjunctival  layer. 

The  lower  portion  of  the  conjunctiva,  where  it  takes  its 
origin  from  the  margin  of  the  lid,  is  quite  smooth  ;  but  near 
the  upper  edge  of  the  tarsus  it  becomes  more  or  less  infiltrated 
with  lymph- cells,  and  is  thrown  into  numerous  folds,  which 
have  sometimes  been  mistaken  for  glands.  The  epithelial  ele- 
ments of  this  part  vary  much  in  shape ;  in  general  there  are 
two  layers :  a  superficial  one,  composed  of  cylindrical  bodies 
which  are  a  continuation  of  the  superficial  strata  of  the  skin, 
and  a  deeper  one  of  small,  round  cells,  representing  the  changed 
cylindrical  elements  of  the  Malpighian  layer  or  rete  mucosum. 

The  tunica  propria  consists  of  fine  connective- tissue  fibres, 
in  which  a  few  elastic  fibrillse  are  interspersed.  The  subcon- 
junctival layer  resting  immediately  upon  the  tarsus  is  very 
thin.  That  part  of  the  conjunctiva  forming  the  fornix  has  an 
abundant  subconjunctival  tissue,  which  is  composed  of  loose 
elastic  fibres  and  vessels  ;  the  epithelial  layers  are  also  thicker 
here,  and  small  racemose  glands,  supposed  to  secrete  mucus, 
are  also  found  there. 

On  the  conjunctiva  covering  the  bulb  the  epithelium  con- 
tains here  and  there  the  large  mucus-cells  corresponding  to 
the  goblet- cells  of  the  intestines.  It  gradually  begins  to  change 
its  character  and  passes  over  into  the  variety  which  is  seen  in 


THE   EYE.  331 

the  cornea,  and,  in  fact,  is  continuous  with  it.  The  tunica 
propria  has  an  abundant  supply  of  blood-vessels,  and  is  loosely 
connected  with  the  sclera  by  fibres,  which  become  more  numer- 
ous and  firm  in  the  vicinity  of  the  corneal  margin. 

The  nerves  of  the  conjunctiva  may  be  seen  by  cutting  small 
pieces  of  fresh  conjunctiva  from  a  pig  or  calf  and  examining 
them  in  aqueous  humor,  or  in  a  1  per  cent,  aqueous  solution  of 
common  salt — care  being  taken  to  support  the  cover-glass  at 
the  sides,  in  order  to  avoid  pressure.  The  nerve-fibres  can  then 
be  seen  passing  under  the  epithelium  ;  they  can  be  distin- 
guished with  certainty  by  their  annular  constrictions  (anneaux 
constricteurs) ;  after  penetrating  a  short  distance,  however, 
they  lose  their  medullary  sheath  and  form  open  networks 
under  the  epithelium  ;  a  few  fibres  find  their  way  toward  the 
surface  between  the  epithelial  cells. 

The  gold  method  is  of  special  use  in  exposing  the  finer 
nerve-branches.  The  question  of  the  manner  in  which  the 
nerves  ultimately  end  is  still  a  point  in  dispute. 

The  lymph-spaces  of  the  conjunctiva  are  quite  numerous, 
especially  near  the  corneal  border ;  here  they  are  narrow,  and 
finally  pass  forward  to  unite  with  the  lymph-spaces  of  the  cor- 
nea, from  which  they  can  be  injected  by  means  of  a  solution 
of  alkanet-root  in  turpentine.1 

The  normal  conjunctiva  does  not  have  any  true  papillae,  but 
on  the  tarsal  portion  the  surface  often  has  small  papilliform 
projections  covered  with  epithelium. 

The  cornea. — This  tunic  is  covered  with  stratified  epithe- 
lium (a),  comprising  layers  of  flat,  serrated,  and  cylindrical 
cells.  Directly  beneath  these  is  the  anterior  limiting  or  Bow- 
man's membrane  (b) ;  this  is  a  clear,  homogeneous  stratum, 
which  differs  from  the  substantia  propria  of  the  cornea  only  in 
containing  no  lymph-spaces  or  cells.  It  can  be  divided  up 
into  the  same  line  fibres  as  the  cornea  itself,  and  its  inner  bor- 
der has  no  distinct  limit,  the  fibres  passing  directly  into  the 
corneal  tissue ;  when  this  layer  has  been  destroyed,  as  by  a 
perforating  ulcer  or  wound,  it  is  not  regenerated. 

The  substantia  propria  of  the  cornea  (&,  c)  is  made  up  of 
lamellae,  like  the  leaves  of  a  book ;  these  lamellae,  which  at 
first  appear  homogeneous,  can  be  separated  into  fine  fibres,  just 


See  chapter  on  General  Methods. 


332 


MANUAL    OF   HISTOLOGY. 


like  other  connective-tissue  membranes,  by  dissolving  out  the 
cementing  substance  in  a  10  per  cent,  solution  of  common  salt. 
With  the  exception  of  tlivfibrcearcuatce,  which  curve  for- 
ward through  several  strata  in  the  anterior  portions  of  the 
cornea,  the  fibres  pursue  the  same  direction  as  the  layers  ;  but, 
although  most  of  the  fibres  run  parallel  to  the  surface  of  the 
cornea,  yet  they  may  have  a  different  direction  in  each  layer, 


FIG.  151.— Meridional  section  through  the  cornea  of  the  human  adult,  from  an  eye  hardened  in  Mill- 
er's fluid.     The  section  was  colored  with  carmine,  and  made  transparent  by  the  oil  of  cloves. 

so  that  when  viewed  from  above  the  fibres  will  appear  to  cross 
one  another.  This  explains  the  formation  of  the  stellate  fig- 
ures which  are  sometimes  observed  after  the  injection  of  fatty 
substances  into  the  cornea,  or  by  the  infiltration  of  bacteria 
between  the  fibrils. 

In  the  interfibrillar  material  are  found  the  lymph- canals 
and  spaces,  which  contain  the  fixed  corneal  corpuscles  (Fig. 
152).  These  spaces  are  stellate  and  broad  when  seen  from  above, 
but  thin  and  spindle-shaped  on  side  view ;  they  have  numer- 
ous branches  and  branchlets  given  off  from  them  at  right 
angles  (lymphatic  channels)  (Fig.  152,  A).  The  spaces  and 
branches  usually  lie  in  the  plane  of  the  lamellae,  anastomose 
freely  with  one  another,  and  are  filled  with  the  corneal  corpus- 
cles and  lymph  (Fig.  152,  B). 


THE    EYE. 


333 


In  life  these  fixed  bodies  nearly  fill  the  lymph-spaces  and 
conform  to  their  size  and  shape  ;  they  are  flat  corpuscles,  usu- 
ally nucleated,  and  have  short,  sharp-pointed  processes,  which 
pass  out  into  the  minute  lymph-canals.  In  the  lymph-spaces 
of  the  cornea  are  also  found,  even  in  normal  conditions,  a  few 
migratory  cells,  resembling  white  blood-corpuscles ;  they  are 
very  numerous  when  the  cornea  has  been  irritated,  and  can 
be  seen  in  a  frog's  cornea,  which 
has  been  kept  five  to  fifteen 
minutes  in  serum  or  aqueous 
humor  in  a  moist  chamber,  and 
examined  without  pressure  on 
a  warm  slide. 

Beneath  the  subs  tan  tia  pro- 
pria  of  the  cornea  we  find  the 
posterior  limiting  layer,  or 
Descemef  s  membrane  (d)  (Fig. 
151).  This  is  transparent,  ap- 
parently homogeneous,  rolls  up 
when  cut,  is  intimately  connect- 
ed with  the  posterior  fibres  of 
the  cornea  proper,  and  is  lined 
on  its  inner  surface  with  endo- 
thelium  (e).  It  contains  no  cel- 
lular bodies,  but,  like  the  anterior  limiting  layer,  can  be  sepa- 
rated into  fibrillse,  and  appears  to  represent  a  concentration  of 
the  corneal  fibres  rather  than  a  separate  structure. 

The  endothelium  is  a  single  layer  of  flat  cells  lining  the 
anterior  chamber.  Blood-vessels  are  found  only  in  the  normal 
cornea  at  the  periphery,  where  they  form  a  fine  network  con- 
necting with  the  conjunctival  and  scleral  vessels. 

The  nerves  enter  the  cornea  at  the  posterior  part  of  the 
periphery ;  they  soon  lose  their  neurilemma  and  medullary 
sheath,  and  pass  forward  obliquely,  as  small  axis-cylinders, 
toward  the  epithelial  layer ;  here  they  divide  up  into  branch- 
lets,  often  having  a  ganglionic  enlargement  at  the  point  of  divi- 
sion. Under  the  epithelium  these  delicate  fibres  form  a  net- 
work which  sends  some  very  minute  filaments  upward  between 
the  epithelial  cells.  Their  further  course  is  unknown. 

To  separate  the  cornea  into  its  constituent  fibres,  small  pieces 
should  be  soaked  for  twenty-four  hours  in  a  concentrated  pi- 


Fio.  152. -Lymph  spaces  and  canals,  A ;  fixed 
corneal  cell,  partly  filling  these  spaces,  B.  After 
Waldeyer. 


334  MANUAL    OF   HISTOLOGY. 

eric  acid  solution  ;  they  can  then  be  washed  in  water  and  easily 
picked  to  pieces.  In  order  to  see  the  arrangement  of  the  fibrillse 
in  the  different  layers,  the  cornea  of  a  rabbit  should  be  pricked 
with  a  needle  in  several  places ;  then  some  highly  infectious 
fluid,  as  the  exudation  in  puerperal  peritonitis,  is  to  be  brushed 
over  the  surface,  and  in  a  few  days  an  infiltration  will  have 
taken  place  throughout  the  interfibrillar  substance.  We  shall 
then  see  the  lines  of  pus-cells  crossing  one  another  in  different 
directions,  and  sometimes  collections  of  micrococci  forming 
stellate  figures. 

A  very  delicate  preparation  of  the  fixed  corneal  cells  may 
be  made  by  removing  a  fresh  cornea,  and  then  immersing  it 
from  three  to  six  hours  in  aqueous  humor,  in  a  moist  chamber. 
In  examining  it  take  care,  as  before  mentioned,  to  avoid  any 
pressure  upon  the  cover-glass. 

It  is  easier,  however,  to  demonstrate  the  cells  and  lymph- 
spaces  by  staining  with  silver  or  gold.  To  do  this  the  nictitat- 
ing membrane  of  a  live  frog  should  be  cut  off  or  held  to  one 
side  by  an  elevator  ;  the  exposed  cornea  is  then  placed  near  the 
mouth  of  a  test-tube,  in  which  some  water  has  been  raised 
to  the  boiling  point ;  when  the  epithelium  begins  to  appear 
opaque  it  should  be  carefully  wiped  off  with  a  fine  cloth ;  a 
£  per  cent,  aqueous  solution  of  nitrate  of  silver  is  then  applied  ; 
when  the  cornea  has  become  thoroughly  white  by  this  method, 
it  is  to  be  removed,  washed  in  a  weak  solution  of  common  salt, 
placed  in  distilled  water,  and  exposed  to  the  light  until  it  be- 
comes brown.  It  should  then  be  cut  at  the  edges  and  mounted 
in  glycerine.  In  ten  or  fifteen  minutes  it  will  be  transparent 
and  ready  for  examination.  Instead  of  removing  the  epithe- 
lium by  steam,  a  solution  of  silver  nitrate  (-J-  per  cent.)  may  be 
used,  the  lids  being  held  out  of  the  way  until  the  epithelium 
appears  whitish;  this  outer  layer  is  then  removed,  and  the 
same  process  repeated  as  before.  The  substantia  propria  as- 
sumes a  brown  color,  and  the  corpuscles  appear  as  lighter  spaces 
in  it.  The  nuclei  may  be  exposed  by  hsematoxylon. 

The  best  preparations,  both  for  the  lymph-spaces  and  the 
nerves,  are  made  with  chloride  of  gold.  A  fresh  cornea,  pref- 
erably one  from  a  live  pigeon,  is  removed  immediately  after 
decapitation  and  immersed  for  five  minutes  in  lemon- juice, 
then  washed  in  distilled  water,  placed  for  fifteen  minutes  in  a 
1  per  cent,  solution  of  chloride  of  gold,  again  washed,  and  this 


THE   EYE.  335 

time  soaked  for  twenty-four  hours  (well  protected  from  the 
light)  in  a  2  per  cent,  solution  of  formic  acid.  After  another 
washing  in  distilled  water  the  cornea  should  be  cut  in  two  and 
placed  in  glycerine ;  one  portion  can  then  be  separated  into 
thin  layers,  by  tearing  with  tine  forceps  or  needles. 

Examine  in  glycerine  for  the  corneal  corpuscles,  nerves, 
and  lymph-spaces,  which  latter  appear  dark  on  a  light  blue 
or  red  background  ;  or  the  piece  may  be  imbedded  in  wax  or 
some  such  material,  and  sections  made  parallel  to  the  surface 
of  the  cornea.  The  remaining  half  of  the  specimen  is  to  be 
imbedded  or  held  in  liver  or  pith.  Transverse  sections  may 
then  be  made.  These  will  exhibit  on  lucky  sections  the  fine 
plexuses  of  nerve-filaments  under  the  epithelium,  with  occa- 
sional fibres  passing  up  between  the  individual  corpuscles. 
The  different  layers  of  the  cornea  will  be  well  shown,  also  the 
narrow  corneal  cells  (as  seen  on  side  view),  together  with  the 
remains  of  the  endothelial  layer  on  the  inner  surface. 

The  peripheral  portions  of  the  cornea  are  particularly  inter- 
esting. We  have  here  the  transitions  from  cornea  to  conjunc- 
tiva and  sclera,  the  origin  of  the  ciliary  muscle,  the  ligament 
of  the  iris,  and  the  numerous  vessels  of  the  part. 

The  epithelium  of  the  cornea  (a)  forms  a  gradual  transition 
into  the  epithelium  of  the  conjunctiva,  but  the  anterior  limit- 
ing membrane  (Bowman's)  becomes  thinner  as  it  approaches 
the  edge  of  the  cornea,  until  finally  it  merges  with  the  fibres 
of  the  anterior  corneal  layers  into  the  tunica  propria  of  the 
conjunctiva. 

No  sharp  boundary  line  has  been  demonstrated  between 
the  cornea  and  the  sclera.  Under  the  microscope  the  fibres 
appear  to  have  no  distinct  limit ;  the  lymph-spaces  also  of  the 
cornea  are  continued  directly  into  the  sclera,  and  the  scleral 
and  corneal  fixed  corpuscles  are  much  the  same. 

The  posterior  limiting  membrane  (DescemeV  s]  (c),  like  the 
anterior,  becomes  gradually  thinner  and  loses  itself  in  a  small 
bundle  of  scleral  fibres  which  surround  the  edge  of  the  mem- 
brane and  form  the  anterior  support  to  the  ligamentum  pec- 
tinatum  iridis. 

The  endothelium  (Fig.  153  6, )  passes  uninterruptedly  over 
this  ligament  (ef)  and  is  reflected  forward  over  the  anterior  sur- 
face of  the  iris  (e")  to  the  edge  of  the  pupil. 

In  the  ^ngle  between  the  iris  and  cornea,  forming  buttresses, 


336 


MANUAL    OF   HISTOLOGY. 


as  it  were,  to  hold  the  iris  in  position,  is  the  ligament  of  the 
iris  (d),  composed  of  loose  connective  tissue  with  an  abundant 
open  mesh  work,  enclosing  spaces  (Fontantfs  spaces),  (f),  which, 
on  the  one  hand,  connect  with  the  anterior  chamber  by  small 
openings  lined  with  endothelium,  and  on  the  other  with  the 
lymph-spaces  of  the  cornea  and  sclera,  as  may  be  shown  by 
injecting  a  solution  of  aniline  blue  into  the  anterior  chamber. 


FIG.  153. — Corneal  margin  from  a  meridional  section  of  the  human  eye :  a.  a',  external  epithelium  of 
the  cornea  ;  a',  a",  epithelium  of  the  conjunctiva  bulbi ;  6,  &'.  &',  corneal  tissue ;  ft7,  &',  &",  &",  sclerotica  ; 
fc,  *,  conjunctiva;  v,  v',  canal  of  Schlomm;  c,  c',  membrane  of  Descemet;  d,  process  of  the  iris:  «/",  iris;  e, 
endothelium  of  the  membrane  of  Descemet;  e'.  e\  e',  of  the  ligamentum  pectinatum  iridis  ;  e'\  e'\  e",  of 
the  iris ;  /,  mesh  work  of  the  space  of  Fontana ;  m,  musculus  oiliaris. 


At  the  inner  part  of  the  sclera,  close  to  its  junction  with  the 
cornea  and  the  ligament,  is  the  canal  of  Schlemm  (v, a'),  a  ring- 
shaped  passage,  oval  on  section.  It  is  lined  with  a  single  ]ayer 
of  endothelium,  varies  in  size  in  different  specimens,  often  ap- 
pearing as  if  divided  into  two  parts,  and,  according  to  Wal- 
deyer,  probably  connects  with  the  anterior  chamber  and  also 
with  the  scleral  veins. 

Through  this  passage  and  Fontana? s  spaces  the  fluid  of  the 
anterior  chamber  is  supposed  to  escape  from  the  globe,  and  it 
is  worthy  of  note  that  in  glaucoma,  with  increased  intra-ocular 
tension,  we  find  the  iris  attached  to  the  periphery  of  the  cor- 


THE   EYE.  337 

nea  over  a  circular  space  which  would  entirely  cover  these 
probable  channels  of  exit. 

Preparations  of  these  parts  can  be  made  from  eyes  which 
have  been  placed  in  Miiller's  fluid  while  quite  fresh  and  al- 
lowed to  remain  in  it  three  to  four  weeks,  the  fluid  being  re- 
newed from  time  to  time.  Hsematoxylon  is  well  adapted  for 
coloring  them,  and  they  may  be  preserved  in  glycerine. 

The  solera. — In  the  sclera  we  find  the  same  minute  struc- 
tures as  in  the  cornea,  i.e.,  bundles  of  fibres,  cementing  sub- 
stance, lymph-spaces,  and  fixed  corpuscles.  The  fibres,  how- 
ever, are  not  laminated,  as  in  the  cornea,  but  run  in  various 
directions,  weaving  a  very  dense  tissue,  so  that  the  lymph- 
canals  have  a  correspondingly  tortuous  course. 

Chemically  there  is  a  difference  between  the  two,  as  the 
sclera  is  found  to  yield  on  boiling  a  true  connective-tissue 
gelatine ;  the  cornea,  on  the  other  hand,  a  substance  resem- 
bling chondrine.  We  find  also  in  the  sclera,  near  the  foramen 
for  the  optic  nerve,  a  few  pigment-cells. 

The  sclera  is  covered  by  the  conjunctiva  from  the  corneal 
border  to  the  insertion  of  the  recti  muscles,  and  the  fibres  of 
the  subconjunctival  tissue  pass  directly  into  it.  From  the  en- 
trance of  the  optic  nerve  to  these  muscular  insertions,  and  even 
passing  up  between  them,  the  scleral  portions  of  Tenon's  cap- 
sule form  the  covering,  which  consists  of  delicate  filaments  of 
connective  tissue  passing  directly  into  the  sclera  itself.  On  the 
inner  surface  the  sclera  is  covered  with  a  large-celled  endothe- 
lium  lining  the  perichoroidal  space.  At  the  round  opening 
for  the  entrance  of  the  optic  nerve,  the  outer  fibres  of  the  optic 
nerve  sheath  pass  directly  into  the  outer  scleral  layers ;  the 
inner  portions  of  the  sheath  partly  mingle  with  the  inner 
layers  of  the  sclera,  and  partly,  after  the  addition  of  some  true 
scleral  fibres,  form  the  lamina  cribrosa,  a  fine,  sieve-like  net- 
work of  fibrous  tissue,  which  stretches  across  the  opening  in 
the  sclera  on  a  level  with  its  inner  surface.  This  lamina  can 
be  easily  shown  in  specimens  where  the  delicate  nerve-fibres 
.which  pass  through  its  openings  have  been  macerated  out. 

The  sclera  is  perforated  in  the  equatorial  region  by  the 
trunks  of  the  vena  vorticosce ;  they  are  accompanied  by  the 
lymph-vessels  which  form  the  connection  between  the  pericho- 
roidal  and  Tenon's  lymph-spaces.  The  direction  of  the  canal 
through  which  they  pass  is  so  oblique  that  it  is  supposed  to  be 


338 


MANUAL    OF    HISTOLOGY. 


easily  contracted  in  diameter  by  any  increase  in  intra-ocular 
pressure. 

The  arteries  of  the  sclera,  with  their  thick  adventitial  coats, 
the  peculiar  sheaths  of  the  veins  and  capillaries,  as  also  the 
nerves,  are  best  studied  in  hematoxylon  preparations.  A  solu- 
tion of  silver  nitrate  (a  quarter  to  one  per  cent.)  will  expose 
the  endothelial  cells,  while  sections  of  the  tissue  may  be 
made  from  specimens  preserved  in  alcohol  or  Miiller's  fluid. 

The  tunica  vasculosa,  consisting 
of  the  choroid,  ciliary  body,  and 
iris,  forms  one  continuous  mem- 
brane through  which  the  principal 
blood-supply  of  the  eye  is  carried. 
The  choroid.  —  This  tunic  lines 
the  sclera  from  the  entrance  of  the 
optic  nerve  to  the  junction  of  sclera 
and  cornea,  and  is  united  to  it  at 
those  points  ;  over  the  remaining 
portion  there  is  a  loose  connection 
formed  by  scattered  fibres  and  the 
numerous  vessels  and  nerves  which 
pass  through  the  sclera  to  the  clio- 
roid. The  meshes  of  the  open 
network  between  the  layers  of 
the  choroid  and  the  sclera  form 
lymph-sacs  —  the  perichoroidal 
spaces  —  which  connect  with  the  sac 
enclosed  in  Tenon's  capsule,  and 
this  in  turn  unites  with  the  su- 
pra-vaginal  space  surrounding  the 

,  ,  „       ,  .  an 

Slieatll     OI     the     ODtlC     nerV6.          1116 


ret- 


FIG.  154.  -sciera,*;  choroid 

:ma,  ?•;    perichoroidal  space,  pdi;    lamina 

Buprachoroidea,  sc;    lamina  chorio-capilla- 

iris,  cc  \  lamina  vitrea,  »  ;  layer  of  pigment- 

cells  between  choroid  and  retina,!?.    After       cllOrOld    COnSlStS    Of    Several  layers, 

.Merkel.  v          7 

with  limits  not  distinctly  marked. 

The  lamina  suprachoroidea  (Fig.  154,  sc)  lies  next  the 
.sclera,  and  consists  of  fine  elastic  and  connective-tissue  fibres, 
holding  in  their  meshes  pigmented  and  transparent  cells: 
the  first  are  stellate,  often  with  projecting  arms  by  which 
several  are  joined  together  ;  the  latter  resemble  lymph-cor- 
puscles. 

The  layer  of  large  vessels  is  traversed  by  branching  arteries 
and  veins  ;  between  them  are  numerous  pigmented  corpuscles, 


THE   EYE.  339 

while  the  whole  is  held  together  by  the  firm  connective-tissue 
network  which  extends  throughout  the  entire  choroid. 

The  lamina  chorio-capillaris  (cc)  consists  of  a  network  of 
fine  vessels  interspersed  with  pigment,  and  extends  over  the 
whole  inner  portion  of  the  choroid. 

The  vitreous  layer  (v)  is  very  closely  connected  with  the 
lamina  chorio-capillaris ;  though  it  appears  homogeneous, 
fibres  may  be  detected  in  it  after  long  maceration  in  a  ten  per 
cent,  solution  of  common  salt.  Where  this  layer  covers  the  cil- 
iary processes  the  surface  is  no  longer  smooth,  but  has  fine, 
elevated  ridges  upon  it ;  here  the  membrane  also  is  thicker, 
and  is  more  easily  affected  by  reagents. 

The  dense  lamina  of  hexagonal  pigment-cells  between  the 
choroid  and  retina  has  sometimes  been  classed  with  the  former, 
although*  it  belongs  more  properly  to  the  retina. 

The  long  and  short  posterior,  and  the  anterior  ciliary  arte- 
ries, furnish  the  numerous  blood-vessels  which  constitute  the 
great  mass  of  the  choroid. 

The  short  posterior  ciliary  arteries,  four  to  six  in  number, 
give  off  some  twenty  branches  which  penetrate  the  solera, 
pursuing  a. straight  course  near  where  the  optic  nerve  enters  ; 
then,  continuing  their  course  in  a  tortuous  manner,  they  divide 
into  fine  networks  which  supply  the  greater  part  of  the  lamina 
chorio-capillaris.  About  the  entrance  of  the  optic  nerve  they 
also  form  a  network  of  fine  vessels,  and  even  send  occasional 
branches. to  anastomose  with  vessels  from  the  sheath  and  cen- 
tre of  the  optic  nerve. 

The  two  long  ciliary  arteries  penetrate  the  sclera  in  a  very 
oblique  course,  a  little  anteriorly  to  those  last  mentioned,  and 
in  the  horizontal  meridian ;  they  pass  forward  in  the  outer 
lamina  of  the  choroid  without  branching  until  they  reach  the 
ciliary  muscle ;  here  they  divide,  and  penetrating  the  muscle, 
form  near  the  periphery  of  the  iris  a  circle  (circulus  arteriosus 
iridis  major)  by  uniting  with  the  artery  of  the  opposite  side. 

The  anterior  ciliary  arteries,  eight  to  ten  in  number,  arising 
from  muscular  branches  of  the  ophthalmic  artery,  penetrate 
the  sclera  near  the  insertion  of  the  recti  tendons ;  they  also 
unite  with  the  circle  just  described,  which  forms  the  principal 
distributing  point  for  the  vessels  of  the  iris  and  ciliary  body. 
From  this  circle  also  are  sent  back  a  few  small  branches  to  unite 
with  the  choroidal  capillaries,  and  there  is  formed  the  sole  con- 


340  MANUAL    OF   HISTOLOGY. 

nection  between  the  short  posterior  or  choroidal  arteries  pro- 
per and  those  which  supply  the  circulus  arteriosus.  A  small 
amount  of  the  blood  which  returns  from  the  capillaries  of  the 
choroid,  ciliary  body  and  iris  finds  its  exit  from  the  eyeball 
through  the  veins  accompanying  the  anterior  and  posterior 
ciliary  arteries,  but  by  far  the  larger  part  is  collected  by  the 
large  veins  in  the  outer  layers  of  the  choroid  (venae  vorticosse), 
converging  so  as  to  form  four  or  six  great  trunks,  which  perfo- 
rate the  sclera  obliquely  in  the  equatorial  region,  and  empty 
into  the  ophthalmic  vein. 

The  long  and  short  ciliary  nerves  supply  the  tunica  vascu- 
losa  with  fibres  from  the  third  and  fifth  pair  and  the  sympa- 
thetic. The  long  nerves,  two  or  three  in  number,  are  branches 
of  the  nasal  division  of  the  ophthalmic  nerve  ;  the  short,  ten  to 
fifteen  in  number,  arise  from  the  ciliary  ganglion.  These  nerves 
penetrate  the  sclera  near  the  optic  nerve,  and  then,  passing  for- 
ward on  the  outer  portion  of  the  choroid,  form,  in  the  ciliary 
muscle,  a  fine  plexus  with  ganglionic  corpuscles  at  the  nodal 
points  of  the  meshes ;  from  this  plexus  fibres  are  distributed 
to  the  cornea  and  iris. 

At  the  junction  of  the  anterior  and  middle  thirds  of  the 
eyeball  the  choroid  undergoes  a  change,  the  membrane  be- 
comes thinner,  the  capillaries  turn  back  toward  the  veins,  only 
a  few  vessels  continuing  forward  in  a  straight  course. 

In  this  region  the  retina  also  undergoes  a  change  and  loses 
all  its  nervous  elements,  the  connective  tissue  supporting  fibres 
alone  being  continued  forward  under  the  name  of  the  pars  cili- 
aris  retinae.  The  very  narrow  zone  between  the  points  where 
these  changes  occur  and  the  irregular  line  formed  by  the  begin- 
ning of  the  ciliary  processes  is  called  the  orbiculus  ciliaris^ 
and  the  line  of  origin  of  these  processes  the  ora  serrata. 

The  ciliary  body. — Crossing  the  orbiculus,  the  choroid  is 
seen  raised  in  radial  folds,  some  seventy  in  number,  which  in- 
crease in  size  until  they  reach  the  thickness  of  a  millimetre. 
This  increase  is  caused  by  the  development  of  smooth  muscular 
fibres  in  addition  to  the  usual  constituents  of  the  choroid. 

These  fibres  arise  just  behind  the  canal  of  Schlemm,  from 
the  sclera  and  cornea ;  passing  backward,  they  together  form 
a  ring,  which  on  section  appears  as  a  right-angled  triangle, 
with  the  base  turned  toward  the  anterior  chamber,  and  the  hy- 
pothenuse  toward  the  vitreous  (Fig.  155). 


THE   EYE. 


341 


This  triangle  consists  largely  of  the  fibres  of  the  ciliary  mus- 
cle, which  are  divided  into  meridional  fibres,  or  those  which 
occupy  the  side  next  the  sclera,  and  radial  fibres,  which  pass 


FIG.  155.— Section  through  the  ciliary  region  of  a  hypermetropic  eye.    Ivanof. 

from  the  point  of  origin  to  the  hypothenuse  ;  the  circular  fibres 
of  Miiller's  muscle  lie  next  to  the  base  of  the  triangle,  and  are 
concentrically  arranged. 

In  highly  myopic  eyes  the  meridional  and  radial  fibres 


PIG.  156.— Section  through  the  ciliary  region  of  a  myopic  eye.    Ivanof. 

are  strongly  developed  (Fig.  156),  while  the  circular  fibres  are 
Scarcely  seen,  and  the  angle  of  the  ciliary  body  at  the  point  of 
origin  is  changed  from  a  right  to  an  acute  angle. 


342  MANUAL    OF   HISTOLOGY. 

In  very  hypermetropic  eyes,  on  the  contrary,  tlie  circular 
fibres  are  abundantly  developed  (Fig.  155),  the  meridional  fibres 
are  shorter,  while  the  angle  at  the  point  of  origin  of  the  mus- 
cle becomes  somewhat  obtuse,  so  that  by  these  changes  one  can 
determine,  even  in  a  microscopic  section,  what  considerable 
refractive  error  the  eyes  have  had. 

The  meridional  fibres  are  either  prolonged  some  distance 
into  the  stroma  of  the  choroid  and  end  in  a  delicate  fringe,  or 
they  terminate  at  the  anterior  and  outer  layers  of  this  mem- 
brane in  stellate  knots  with  fine  anastomosing  branches. 

The  radial  fibres  form  a  looser  network  than  the  last,  but 
also  have  the  same  terminal  interlacement  of  their  fibres ;  the 
circular  fibres  form  fewer  anastomoses,  and  only  those  bundles 
which  lie  next  to  the  radial  fibres  are  extensively  connected 
with  them. 

The  nerves  of  the  ciliary  body  are  derived  from  the  plexus 
formed  in  its  stroma  by  the  ciliary  nerves ;  the  vessels  are 
largely  supplied  from  the  circulus  iridis  major,  lying  in  the  an- 
terior part  of  the  body. 

The  iris  arises  from  the  anterior  side  of  the  ciliary  body, 
and  from  the  connective  tissue  surrounding  the  fibres  of  the 
ciliary  muscle  ;  it  is  also  attached  to  the  cornea  and  sclera  by 
the  ligamentum  pectinatum.  (See  Fig.  153). 

It  consists  of  a  loose  connective-tissue  stroma,  which  sup- 
ports a  rich  vascular  network,  a  complete  muscular  structure, 
and  the  nerves.  It  is  covered  anteriorly  by  a  continuation  of  the 
endothelium  of  the  cornea,  and  posteriorly  by  a  thick  layer  of 
pigment-cells  continuous  with  those  which  line  the  ciliary  body. 
The  vessels  arise  from  the  circulus,  have  adventitial  coats  which 
are  thick  in  proportion  to  their  calibre,  and  pass  radially  to 
the  margin  of  the  pupil,  where  they  form  a  network  of  fine 
capillaries,  the  circulus  arteriosus  iridis  minor,  ending  final- 
ly in  veins  which  return  in  the  same  general  direction  as  the 
arteries,  but  lie  beneath  them,  emptying  finally  into  the  venae 
vorticosse. 

Near  the  margin  of  the  pupil,  and  forming  a  ring  about 
it  1  mm.  in  breadth  by  TV  mm.  in  thickness,  is  the  sphincter 
muscle  of  the  iris.  It  is  composed  of  unstriped  muscular  tissue, 
and  is  situated  in  the  posterior  portion  of  the  iris. 

The  dilator  muscle,  at  its  inner  border,  is  in  close  connection 
with  the  sphincter,  and  its  fibres  run  radially  to  the  periphery 


THE   EYE.  343 

of  the  iris,  where  they  are  woven  into  a  thick  anastomosing 
circle. 

The  nerves  of  the  iris  are  derived  from  the  ciliary  plexus ; 
at  the  periphery  they  divide  and  scatter  in  various  directions : 
the  pale  fibres  to  the  posterior  layers,  forming  a  fine  network 
about  the  dilator  muscle;  the  fibres  with  a  medullary  sheath 
to  the  anterior  portion ;  another  set  supplies  the  sphincter 
muscle — these  being,  in  the  order  of  description,  the  branches 
possibly  of  the  sympathetic,  sensory,  and  of  the  third  pair. 

The  posterior  surface  of  the  iris,  which,  near  the  pupil,  rests 
upon  the  anterior  capsule  of  the  lens,  is  covered  with  a  thick 
layer  of  densely  pigmented  cells,  the  uvea,  which  can  rarely  be 
so  separated  as  to  determine  their  shape,  and  which  appear  to 
have  no  distinct  limiting  membrane  behind  them. 

This  layer  extends  from  the  pupil,  where  it  meets  the  endo- 
thelium  of  the  anterior  surface,  back  to  the  pigment  of  the 
ciliary  body,  with  which  it  is  continuous  and  from  which  it  can 
be  distinguished  by  having  no  connective  tissue  covering  it. 
The  pigmented  cells,  which  are  more  or  less  thickly  scat- 
tered through  the  stroma  of  the  iris,  determine  the  color  of 
the  anterior  surface. 

Transverse  sections  through  the  sclera  and  choroid  are  best 
made  from  eyes  hardened  in  Muller's  fluid.  An  eye  which  has 
been  injected  with  colored  gelatine,  introduced  through  the 
aorta  after  that  vessel  has  been  tied  beyond  the  carotids,  will 
show  the  fine  meshes  of  the  chorio-capillaris,  when  the  pigment- 
layer  covering  the  choroid  has  been  brushed  away  under  gly- 
cerine. Such  injections  are  best  made  on  albinotic  rabbits. 

Good  sections  of  the  ciliary  body  can  be  made  from  eyes 
hardened  in  alcohol  or  Muller's  fluid,  and  the  blood-vessels 
can  be  easily  seen  in  injected  specimens.  The  muscular  tissue 
of  this  body  and  the  iris  may  be  examined  in  specimens  treated 
with  a  30  to  40  per  cent,  solution  of  potash.  Carmine  may 
then  be  used  to  color.  The  vessels  of  the  iris  are  best  seen  in 
the  eyes  of  a  young  albino  rabbit,  injected  with  colored 
glycerine  or  Berlin  blue. 

The  retina  lines  the  whole  inner  surface  of  the  choroid  as 
far  as  the  ora  serrata ;  it  is  composed  of  nervous  elements, 
connective  tissue,  and  blood-vessels. 

The  following  division  into  well-marked  layers  from  within 
outward  has  been  generally  adopted.  (See  Fig.  157). 


344 


MANUAL    OF    HISTOLOGY. 


a,  membrana  limitans  interna. 
Z>,  optic  nerve  fibre-layer. 

c,  ganglion-cell  layer. 

d,  inner  granular  layer. 

e,  inner  nuclear  layer. 

^  outer  granular  layer. 
<7,  outer  nuclear  layer. 
7i,  membrana  limitans  externa. 
i,  layer  of  rods  and  cones. 
Pigment  layer. 

The  fibres  of  the  optic  nerve  generally  lose  their  medullary 
sheath  at  the  lamina  cribrosa,  and  proceed 
thence  as  naked  axis- cylinders  through  the 
opening  in  the  choroid  to  the  level  of  the 
retina,  where  they  spread  over  its  entire  in- 
ner surface  to  form  the  nerve-fibre  layer, 
which  is  thick  in  the  vicinity  of  the  nerve, 
but  gradually  decreases  as  it  approaches 
the  ora  serrata,  where  it  ends. 

At  the  macula  lutea  the  fibres  do  not 
form  a  distinct  layer,  but,  curving  toward 
this  spot  from  above  and  below,  are  lost 
in  the  layer  of  ganglion-cells,  either  entering 
them  or  passing  on  to  the  inner  granular 
layer. 

The  ganglion-cell  layer  consists  of  large 
branching  cells  in  most  places  but  one  row 
deep,  though  near  the  macula  there  may 
be  two  or  more  layers.  They  are  very 
transparent,  have  no  visible  cell-wall,  and 
are  provided  with  a  varying  number  of  pro- 
jecting arms  ;  when  fresh  they  contain  fine 
granular  matter  with  a  clear,  large  nuclei 
and  nucleoli,  and  appear  finely  fibrillated. 

They  receive  an  axis-cylinder  on  their 
inner  side,  and  on  the  outer  send  out 
branches  which  ultimately  divide  into  fine  fibrillae,  and  are 
lost  at  the  inner  granular  layer  in  a  tangled  network.  It  is 
probable,  however,  that  some  of  these  fibres  are  connected 
with  the  cells  of  the  inner  nuclear  layer. 

The  inner  granular  layer  partly  surrounds  the  ganglion- 


FIG.  157. — Transverpe  sec- 
tion of  the  retina.  After  Ze- 
hender. 


THE    EYE.  345 

cells  and  forms  a  sort  of  spongy  network  between  these  and 
the  inner  nuclear  layer ;  its  composition  is  still  a  matter  of 
doubt,  but  it  appears  to  be  made  up  of  a  more  or  less  homo- 
geneous substance,  in  which  are  numerous  fine  openings  filled 
with  some  material  of  a  peculiar  refractive  power.  It  does  not 
belong  to  the  nervous  substance  of  the  retina,  and  when  placed 
in  a  10  per  cent,  solution  of  common  salt,  dissolves, leaving  the 
supporting  connective-tissue  fibres  unaffected. 

The  inner  nuclear  layer  is  made  up  of  numerous  oval  cells 
with  large  nuclei ;  they  belong  mostly  to  the  nervous  tissue, 
but  scattered  among  them  are  also  cells  of  the  supporting  con- 
nective-tissue framework. 

The  nerve-cells  resemble  small  bipolar  ganglion-cells,  hav- 
ing two  fine  processes,  the  inner  of  which  probably  connects 
with  the  ganglion-cell  layer,  or  directly  with  the  optic  nerve 
fibres.  Near  the  macula  these  cells  are  more  numerous  ;  to- 
ward the  ora  serrata  they  gradually  decrease  in  number. 

Next  comes  the  outer  granular  layer,  a  thin  stratum  re- 
sembling the  inner  in  appearance  and  composition ;  here  the 
fine  fibres  from  the  outer  and  inner  nuclear  layers  become  lost 
in  a  tangled  mass. 

Between  this  layer  and  the  membrana  limitans  externa  is 
the  outer  layer  of  nuclei,  made  up  of  a  number  of  oval  cells, 
connected  more  or  less  closely  with  the  inner  ends  of  the  rods 
and  cones. 

The  larger  nerve-fibres,  which  pass  through  the  outer  gran- 
ular layer,  are  joined  to  the  nuclei  of  the  cones,  which  lie  di- 
rectly within  the  membrana  limitans  and  are  connected  to  a 
prolongation  of  the  base  of  the  cones  themselves.  The  smaller 
fibres  pass  to  the  nuclei  of  the  rods,  which  form  an  irregular 
layer  at  varying  distances  from  the  limiting  membrane,  and 
from  which  fine  tangled  fibres  pass  to  the  base  of  the  rods. 
These  nuclei  resemble  those  of  the  inner  layer ;  they  con- 
tain a  small  amount  of  granular  matter  with  a  nucleus  and  nu- 
cleolus,  and  sometimes  exhibit,  as  the  result  of  post-mortem 
changes,  peculiar  transverse  stripes. 

Directly  beyond  the  membrana  limitans  externa,  and  rest- 
ing upon  it,  are  tlie  rods  and  cones,  each  composed  of  an  outer 
'  and  inner  member. 

The  rods  are  small,  cylindrical  bodies  of  high  refractive 
power ;  when  fresh  they  appear  homogeneous,  but  with  the 


346  MANUAL    OF   HISTOLOGY. 

beginning  of  decomposition,  which  occurs  very  quickly,  the 
inner  half  appears  as  if  filled  with  a  finely  granular  substance, 
while  the  outer  exhibits  transverse  striations,  and  finally 
breaks  up  into  small  disks,  which  can  only  be  distinguished 
from  those  of  the  outer  segment  of  the  cones  by  their  red  color 
(visual  purple  of  Kuhne),  which  soon  fades  on  exposure  to 
light. 

The  inner  segment  of  the  cones  is  larger  than  that  of  the 
rods  ;  it  tapers  rapidly  toward  the  outer  part,  where  it  is  filled 
with  a  peculiar  oval-shaped  body  ;  the  outer  segment  does  not 
equal  that  of  the  rods  in  height,  but  divides  into  similar  disks. 

The  pigment-layer,  in  which  the  ends  of  the  rods  and  cones 
are  imbedded,  consists  of  a  single  layer  of  hexagonal  cells, 
more  densely  pigmented  in  the  part  next  the  retina,  and  by 
some  observers  said  to  be  provided  with  fine  processes,  which 
are  lodged  between  the  rods  and  cones.  This  pigment  is  more 
dense  at  the  macula  and  varies  with  the  color  of  the  person, 
being  most  abundant  in  negroes,  whereas  it  is  absent  in  albi- 
nos ;  from  this  layer,  according  to  Kuhne,  the  visual  purple 
of  the  rods  is  reproduced. 

At  the  macula  lutea,  which  is  situated  a  little  to  the  outer 
side  of  the  entrance  of  the  optic  nerve,  the  ganglion-cell  and 
inner  nuclear  layers  have  their  greatest  thickness.  The  fibres 
which  pass  from  the  outer  granular  to  the  outer  nuclear  layer 
are  lengthened  and  run  in  a  more  horizontal  direction  toward 
ihefovea,  which  forms  a  slight  depression  in  the  centre  of  the 
macula. 

Over  this  fovea  the  layers  of  nerve-fibres  and  ganglion-cells 
are  absent,  and  the  other  laminae  become  so  much  thinned 
that  the  membrana  limitans  interna  approaches  nearly  to  the 
nuclear  layer;  the  rods  are  also  absent,  and  the  cones  be- 
come lengthened  and  slightly  convergent. 

The  meiribrana  limitans  interna  lies  between  the  retina  and 
vitreous  body  ;  it  is  a  transparent  homogeneous  structure,  and 
from  its  outer  surface  spring  the  connective-tissue  fibres  which 
form  the  supporting  framework  for  the  nervous  part  of  the 
retina. 

These  fibres  arise  in  the  form  of  thin  fenestrated  plates, 
connected  together  by  numerous  arms ;  they  soon  contract, 
however,  to  smaller  radiating  bands,  which  surround  the  gan- 
glion-cells and  pass  on  to  the  inner  nuclear  layer,  where  they 


THE   EYE.  347 

contain  occasional  nuclei.  From  this  point  they  again  ex- 
pand into  broader  sheets,  which,  after  surrounding  the  outer 
nuclei,  are  united  to  form  the  membrana  limitans  externa. 
This  membrane  lies  just  at  the  base  of  the  rods  and  cones,  and 
it  is  provided  with  numerous  holes,  through  which  those  struc- 
tures pass  ;  from  its  outer  surface  fibres  extend  up  between 
the  rods  and  cones  to  form  supporting  sheaths. 

The  blood-vessels  of  the  retina  come  from  the  arteria  cen- 
tralis  retince,  which  usually  divides  into  two  or  more  branches 
at  the  entrance  of  the  optic  nerve  ;  these  vessels  lie  in  the  layer 
of  nerve-fibres,  and,  arching  above  and  below  the  macula,  give 
off  numerous  fine  branches,  from  which  capillaries  penetrate 
as  far  as  the  inner  nuclear  layer.  The  larger  retinal  vessels  are 
surrounded  by  lymph- spaces,  which  probably  unite  with  those 
of  the  optic  nerve. 

At  the  periphery  the  retina  becomes  much  thinned,  and  at 
the  ora  serrata  the  nervous  elements  are  discontinued,  the  con- 
nective tissue  alone  being  prolonged  over  the  ciliary  body  to 
its  anterior  angle,  thus  forming  the  pars  ciliaris  retinae. 

This  membrane  consists  of  long  cylindrical  cells  of  varying 
shapes ;  they  rest  on  the  pigment  and  are  covered  by  a  thin 
stratum,  which  sends  processes  between  them  and  seems  to  be 
a  prolongation  of  the  membrana  limitans  interna  of  the  retina. 

It  is  very  difficult  to  prepare  good  sections  of  the  retina, 
but  the  following  plan  is  recommended :  enucleate  with  care 
the  eye  of  a  frog  or  some  small  animal,  and  immediately  sus- 
pend it  in  a  well-stoppered  bottle  containing  a  small  bit  of 
solid  osmic  acid  ;  when  sufficiently  hard  the  posterior  portion 
of  the  eye  can  be  cut  in  pieces  and  sections  made  by  imbed- 
ding or  holding  between  pieces  of  liver. 

Another  method  is  to  place  the  eye  unopened  in  Muller'  s 
fluid  for  some  two  weeks,  frequently  changing  the  fluid ;  af- 
terward harden  in  alcohol.  Sections  may  then  be  made  in  the 
same  manner  as  before. 

To  obtain  the  separate  constituents,  place  a  fresh  retina  in 
a  TV  per  cent,  aqueous  solution  of  osmic  acid  for  fourteen  days, 
then  in  glycerine  for  seventeen  days  ;  after  this,  place  a  small 
piece  on  a  slide  in  glycerine,  with  the  cover-glass  so  arranged 
that  no  pressure  is  made  upon  the  specimen  ;  now  tap  gently 
on  the  centre  of  the  glass  until  the  motion  of  the  fluid  causes 
the  retina  to  fall  apart. 


348  MANUAL    OF    HISTOLOGY. 

The  optic  nerve,  after  leaving  the  optic  canal,  passes  through 
the  orbit  surrounded  by  three  coverings,  continuations  of  the 
cerebral  membranes. 

The  dural  coat,  composed  of  dense  connective  tissue  with  a 
few  elastic  fibres,  forms  the  outer  covering  ;  the  fibres  are  at- 
tached to  the  periosteum,  where  the  nerve  leaves  the  bony  canal, 
and  where  it  enters  the  eyeball  they  are  continued  directly  into 
the  outer  layers  of  the  sclera. 

Within  this  covering,  and  separated  from  it  by  a  very  nar- 
row space,  are  the  delicate  fibres  of  the  arachnoidal  coat, 
and  the  lymph-space  between  the  two  is  called  the  subdural 
space. 

Within  the  arachnoidal  coat,  and  separated  from  it  by  a 
wide  lymph-space,  is  the  pial  coat  closely  surrounding  the 
nerve-fibres,  and  sending  processes  of  connective-tissue  be- 
tween their  bundles.  This  membrane  passes  into  the  inner 
layers  of  the  sclera,  and  also  sends  numerous  fibres  to  the  la- 
mina cribrosa.  Its  outer  surface  is  covered  with  endothelium, 
and  between  it  and  the  arachnoid  coat  is  the  subaraclinold 
space,  which  reaches  to  the  inner  layers  of  the  sclera,  and  is 
continuous  with  the  same  space  in  the  brain. 

The  optic  nerve  itself,  closely  surrounded  by  its  vagina 
fibrosa,  passes  forward  through  the  orbit,  receiving  the  central 
artery  and  vein  at  about  15  to  20  mm.  from  the  sclera.  These 
vessels  pass  to  the  centre  of  the  nerve  and  lie  in  a  connective- 
tissue  sheath  until  they  emerge  on  the  inner  surface  of  the  eye- 
ball to  branch  over  the  retina. 

On  cross-sections  of  the  nerve,  bundles  of  connective  tissue 
are  seen  to  pass  inward  from  the  pial  sheath  and  form  a  cross- 
network,  through  the  openings  of  which  the  nerve-fibres  pass. 
On  longitudinal  sections  the  connective  tissue  appears  in 
irregular  fenestrated  sheaths ;  this  tissue  can  also  be  demon- 
strated by  macerating  thick  sections  in  a  J  per  cent,  solution 
of  chromic  acid  and  then  brushing  out  the  nerve-elements. 

These  nerve-filaments  themselves  are  extremely  small,  but 
vary  somewhat  in  size.  They  consist  of  an  axis-cylinder  sur- 
rounded by  its  medullary  sheath;  they  are  grouped  in  large 
bundles  which  pass  through  the  meshes  of  the  connective  tis- 
sue. The  fibres  appear  to  be  held  fogether  by  a  kind  of  homo- 
geneous albuminous  substance — neuroglia,  and  have  on  their 
surface  occasional  nucleated  corpuscles,  distinguished  from 


THE   EYE.  349 

those  of  the  connective  tissue  by  being  larger  and  more  irregu- 
lar in  shape. 

Blood-vessels  are  found  not  only  in  the  centre  of  the  nerve, 
but  also  scattered  through  various  parts  of  the  connective  tis- 
sues. 

At  the  lamina  cribrosa  there  is  an  anastomosis  with  the  ves- 
sels of  the  circle  of  Holler,  which,  coming  from  the  short  poste- 
rior ciliary  arteries,  forms  a  vascular  circle  in  the  sclera,  about 
the  entrance  of  the  optic  nerve. 

Where  the  nerve-fibres  pass  through  the  sieve-like  openings 
of  the  lamina  cribrosa  they  lose  their  medullary  sheath,  and 
from  that  point  pass  on  to  the  nerve-fibre  layer  of  the  retina 
as  transparent  axis- cylinders  ;  but  in  rare  cases  the  sheaths  are 
continued  from  the  optic  disk  some  little  distance  over  the 
retina,  and  are  seen  with  the  ophthalmoscope  as  very  white 
patches  radiating  out  from  the  disk,  or  following  the  vessels 
and  gradually  fading  into  the  general  color  of  the  f undus  by 
a  fine,  fringe-like  border. 

The  vitreous  body  is  a  transparent,  jelly-like  mass,  of  spher- 
ical shape,  with  a  depression  at  the  anterior  part,  in  which  the 
lens  rests.  It  is  bounded  behind  and  on  the  side  by  the  retina, 
in  front  by  the  lens  with  its  attachments,  and  appears  to  have 
no  true  hyaloid  limiting-membrane  of  its  own.  It  is  very  diffi- 
cult to  demonstrate  any  definite  structure  in  this  substance  ; 
toward  the  periphery  it  appears  to  be  arranged  somewhat  in 
concentric  layers,  but  in  the  centre  is  more  homogeneous. 

From  the  optic  disk  to  the  lens  there  is  a  small  canal  about 
1  mm.  wide  in  front  and  spreading  out  behind ;  it  is  lined 
with  very  transparent  cells,  and  filled  with  a  substance  more 
fluid  than  the  rest  of  the  vitreous  ;  it  marks  the  position  of  the 
arteria  hyaloidea^  which  is  usually  obliterated  at  about  the 
seventh  foetal  month. 

The  vitreous  body  also  contains  numerous  corpuscles,  espe- 
cially near  the  periphery  ;  these  consist  of  round  lymph- cells, 
stellate  cells,  with  one  or  more  nuclei,  and  irregular  arms,  and 
of  branching  cells  which  seem  to  have  a  transparent  vesicle 
filling  up  a  part  of  their  interior.  The  vitreous  contains  no 
nerves,  and  after  birth  no  blood-vessels ;  it  may  be  examined 
fresh  or  hardened  in  a  \  per  cent,  solution  of  chromic  acid. 
Sections  may  be  colored  blue  with  aniline,  and  preserved  in 
glycerine. 


350 


MANUAL    OF    HISTOLOGY. 


The  lens  (Fig.  158)  is  a  transparent,  biconvex  body,  sur- 
rounded by  a  structureless,  elastic  capsule,  which  is  thicker  in 
front  where  it  touches  the  iris,  and  thinner  behind  where  it 
rests  in  the  fossa  patellaris  of  the  vitreous. 

The  inner  surface  of  the  anterior  capsule  is  covered  with  a 
single  layer  of  hexagonal  epithelial  cells,  which  become  longer 
near  the  equator  of  the  lens,  and  gradually  pass  over  into  the 
lens-fibre. 

After  birth  these  fibres  consist  of  long,  transparent  tubes,  on 
section  resembling  flattened  hexagons  closely  joined  together 

by  their  serrated  edges;  they  are 
arranged  in  concentric  meridional 
layers  with  their  broad  side  out- 
ward. They  do  not  pass  around 
the  entire  circumference  of  the  lens, 
but  arise  on  the  anterior  surface 
from  three  lines,  which,  uniting  at 
the  axis,  make  a  figure  like  an  in- 
verted Y,  with  the  arms  set  at  an 
angle  of  about  20°  to  each  other ; 
on  the  posterior  surface  this  star 
is  reversed,  the  Y  standing  upright. 
In  adult  life  the  rays  are  more 
numerous,  and  the  fluid  contents 
of  the  tubes  become  more  solid  and 
of  greater  refractive  power,  espe- 
cially toward  the  centre  of  the  lens. 
On  a  meridional  section  of  the 
lens  one  sees  the  concentric  ar- 
rangement of  the  lens-fibres,  and  near  the  equator  a  collection 
of  nuclei  (the  nuclear  zone).  These  nuclei  belong  to  the  lens- 
fibres,  each  one  of  which  originally  had  one,  although  in 
adult  life  they  are  found  more  abundantly  in  the  peripheral 
region. 

The  fibres  of  the  supporting  ligament  of  the  lens  (the  zonula 
ciliaris)  are  attached  to  the  anterior  and  posterior  capsule  near 
the  equator  ;  from  here  they  converge  to  the  apex  of  the  ciliary 
body,  to  which  they  are  fastened. 

The  fibres  form  for  the  most  part  an  anterior  and  posterior 
layer,  and  have  occasional  nuclei,  especially  toward  the  ora 
serrata ;  between  these  layers  is  the  canal  of  Petit,  the  result 


Fio.    158.  —  Meridional    section    through 
axis  of  the  human  lens. 


THE   EYE.  351 

of  post-mortem  changes,  which  quickly  destroy  the  delicate 
fibres  that  ordinarily  lill  this  space. 

Specimens  for  study  may  be  made  in  the  following  way : 
harden  an  eye  for  fourteen  days  in  Muller's  fluid  ;  then  open, 
remove  the  lens,  and  preserve  in  alcohol.  Sections  may  be 
made  in  any  direction ;  they  should  be  colored  with  hema- 
toxylon  and  mounted  in  glycerine. 

To  examine  the  epithelium  under  the  anterior  capsule,  a 
piece  of  capsule  should  be  peeled  oif  from  a  fresh  lens  and  ex- 
amined with  or  without  previous  staining.  Single  lens-fibres 
or  groups  of  fibres  may  be  obtained  by  macerating  a  portion 
of  lens  in  dilute  sulphuric  acid  (£  per  cent.),  or  in  a  -J  per 
cent,  solution  of  chromic  acid,  after  which  it  can  be  easily 
separated  into  its  elementary  parts. 

The  lachrymal  gland  is  situated  under  the  upper  and  outer 
edge  of  the  orbital  wall,  resting  partly  in  a  shallow  fossa  of  the 
frontal  bone,  to  which  it  is  attached  byr  firm  bands  of  connec- 
tive tissue. 

It  is  an  acinous  gland,  divided  into  a  larger  upper  portion 
(glandula  Galeni),  some  20  mm.  long,  10  wide,  and  5  thick,  and 
a  lower  part  of  about  half  the  size  (glandula  Monroi) ;  they  are 
supplied  with  blood  by  a  branch  of  the  ophthalmic  artery,  and 
with  nerves  from  the  fifth  pair. 

The  connective  tissue  which  envelops  the  gland  also  ramifies 
through  its  substance,  dividing  it  into  numerous  small  alveoli, 
in  which  are  the  true  secreting  cells  of  the  gland,  and  from 
which  fine  ducts  pass  out  to  coalesce,  and  finally  discharge  on 
the  free  surface  of  the  conjunctiva  fornicis  at  its  upper  and 
outer  part. 

The  upper  part  of  the  gland  is  quite  dense,  but  in  the  lower 
portion  the  alveoli  are  less  closely  packed,  and  often  near- 
ly surrounded  by  the  orbital  fat.  The  alveoli  are  covered 
by  a  fine  membrane  composed  of  flat  cells  with  numerous 
branches  or  processes,  which  spread  in  various  directions  and 
serve  to  unite  the  cells  of  the  investing  membrane,  and  also  the 
different  alveoli ;  they  form  a  shell  which  is  surrounded  on  its 
outer  side  by  a  distinct  lymph-space,  and  on  its  inner  surface 
is  Jined  by  the  secreting  cells  of  the  gland. 

If  these  lymph-spaces  have  been  injected  with  Berlin  blue, 
and  especially  if  the  blood-vessels  are  injected  with  some  other 
color,  the  arrangement  of  the  lymph-spaces  can  be  very  well 


352  MANUAL    OF   HISTOLOGY. 

seen.  The  openings  from  the  alveoli  are  at  first  lined  with 
fine,  fiat  cells  ;  then,  as  the  tube  grows  larger,  they  assume  the 
character  of  cylindrical  epithelium. 


BIBLIOGRAPHY. 

GRAEFE  u.    SAEMISCH.      Handbuch    der    gesammten    Augenheilktmde.     Vol.    I, 

Leipzig,  1874. 

J.  ORTH.     Cursus  der  normalen  Histologie.     Berlin,  1878. 
A.  ALT.     Lectures  on  the  Human  Eye.     New  York,  1880. 


CHAPTER  XXL 

THE   EAR 
BY  DRS.  WILLIAM    F.  WHITNEY  AND    CLARENCE  J.  BLAKE,  OF   BOSTON. 

FOLLOWING  the  natural  order  are  to  be  considered,  first,  the 
external  ear  with  the  meatus  externus  ;  secondly,  the  middle 
ear  with  the  Eustachian  tube;  and  thirdly,  the  internal  ear 
(membranous  labyrinth  and  cochlea). 

External  ear. — This  includes  the  auricle,  the  meatus  exter- 
nus, and  the  membrana  tympani. 

The  auricle  is  formed  by  a  cartilaginous  plate,  1-2  mm.  in 
thickness.  The  fine  elastic  fibres  of  this  plate,  which  is  of  the 
reticular  variety  of  cartilage,  can  be  traced  into  the  perichon- 
drium,  and  even  into  the  subcutaneous  tissue.  Both  perichon- 
drium  and  subcutaneous  tissue  are  rich  in  elastic  fibres,  the 
latter  varying  greatly  in  amount  in  different  parts  of  the  ear, 
being  very  sparingly  developed  on  the  concave  surfaces,  where 
the  skin  is  closely  adherent  to  the  perichondrium,  and  immov- 
able in  consequence,  but  more  abundant  on  the  convex  sur- 
faces, where  the  skin  is  movable  ;  it  forms,  together  with  the 
fat  enclosed  in  its  meshes,  the  bulk  of  the  lobule. 

The  cutis  covering  the  auricle  is  a  direct  continuation  of 
that  covering  the  face,  and  is  well  provided  with  downy  hairs 
and  sebaceous  glands.  These  latter  reach  their  greatest  devel- 
opment in  the  depressions  of  the  auricle,  especially  the  concha. 

The  external  meatus  consists  of  a  cartilaginous  and  an  os- 
seous portion.  The  former  only  differs  in  structure  from  the 
auricle  into  which  it  passes,  in  the  presence  of  the  ceruminous 
glands.  These  are  tubular  glands,  having  a  coil  at  the  bottom. 
They  consist  of  a  membrana  propria,  on  which  is  a  layer  of 
cubical  epithelium,  and  are  the  analogues  of  the  sweat-glands. 
In  the  osseous  portion  of  the  meatus  the  glands  are  sparingly 
found,  and  the  hairs  are  fewer  and  finer.  Otherwise  there  is 


354  MANUAL    OF    HISTOLOGY. 

no  difference  between  the  two  portions,  except  that  the  carti- 
lage is  replaced  by  bone. 

The  ear  of  a  new-born  child  can  be  easily  removed  with  the 
cartilaginous  part  of  the  meatus,  and  when  hardened  in  Miil- 
ler's  fluid  and  afterward  in  alcohol,  and  imbedded  in  parafnne 
or  hardened  liver,  furnishes  sections  which,  when  colored  with 
hsematoxylon,  show  the  different  relations  very  clearly.  The 
osseous  portion  must  first  be  decalcified  by  allowing  the  bone 
to  hang  freely  in  a  weak  (-J-  per  cent.)  solution  of  chromic 
acid,  often  renewed,  during  several  months.  The  specimens 
are  then  to  be  well  washed,  hardened  in  alcohol,  and  prepared 
as  above. 

At  the  inner  end  of  the  external  meatus,  and  separating  it 
from  the  middle  ear,  is  stretched  the  membrana  tympani.  The 
tympanic  ring,  with  the  membrane  attached  to  it,  is  to  be  care- 
fully separated  from  the  surrounding  parts  by  means  of  bone- 
scissors,  and  placed  for  five  to  fifteen  minutes  in  a  weak  solu- 
tion (two  to  five  per  cent.)  of  formic  or  acetic  acid.  It  shoiild 
then  be  well  washed  in  distilled  water,  and  the  external  layer 
of  epithelium  removed  by  a  camel' s-hair  brush,  arid  finally 
stained  with  hsemotoxylon  and  mounted  in  glycerine.  In  spe- 
cimens thus  prepared  there  are  to  be  distinguished  three  lay- 
ers, viz.:  an  external  or  cuticular  layer,  a  middle  or  fibrous 
layer  (membrana  propria),  and  an  internal  or  mucous  layer. 

The  cuticular  layer  is  composed  of  simple  pavement-epithe- 
lium, without  glands  or  hairs.  It  is  thickest  at  the  periphery, 
and  over  the  handle  of  the  hammer,  and  along  its  edge. 

The  fibrous  layer  (membrana  propria)  consists  of  two  sets 
of  flattened,  spindle-shaped  fibres,  with  long,  thin  connective- 
tissue  corpuscles  imbedded  in  them,  and  which  have  a  close 
analogy  with  the  fibres  of  tendons.  The  outer  series,  lying 
directly  beneath  the  cutis,  radiates  from  the  handle  of  the 
hammer  toward  the  periphery,  while  the  inner  series  circles 
about  the  handle.  At  the  periphery  the  two  series  interlace 
with  each  other  and  with  a  few  fibres  coming  from  the  cuticu- 
lar and  mucous  layers  to  form  the  so-called  tendinous  ring,  in 
which  are  also  to  be  found  a  few  scattered  cartilage-cells.  This 
ring  is  joined  to  the  annulus  tympanicus  by  a  thin  periosteum. 
(The  handle  of  the  hammer  is  joined  to  the  membrana  tympani 
by  a  cartilaginous  formation  which  stands  in  close  relation  to 
the  membrana  propria.  This  is  a  shallow  groove  of  hyaline 


THE    EAR.  355 

cartilage,  in  which  the  handle  of  the  hammer  lies,  kept  in  place 
by  the  mucous  layer  which  passes  over  and  is  firmly  adherent 
to  it ;  the  upper  part  of  this  furrow  ends  in  a  sort  of  cartilagi- 
nous cap,  into  which  the  processus  brevis  fits.)  Transverse 
sections  made  after  hardening  the  membrane  in  Muller'  s  fluid 
and  alcohol,  and  then  imbedding,  give  the  best  idea  of  these 
relations. 

The  inner  or  mucous  layer  is  formed  of  flat  epithelium,  sup- 
ported on  a  reticulated  layer  of  connective  tissue,  and  directly 
continuous  with  the  epithelial  lining  of  the  middle  ear.  The 
arterial  supply  is  furnished  by  a  small  arteriole,  which  follows 
the  handle  of  the  malleolus,  and  gives  off  lateral  capillaries 
anastomosing  with  others  coming  from  small  branches  which 
enter  at  the  periphery.  The  blood  is  collected  into  venous 
trunks  which  pass  out  in  a  similar  manner.  Fine  nerves  are 
said  to  be  found  in  close  connection  with  the  vessels.  They 
apparently  come  from  the  sympathetic  system. 

The  middle  ear. — In  order  to  obtain  a  clear  idea  of  the  rela- 
tions and  structure  of  the  middle  ear  a  fresh  temporal  bone, 
with  the  soft  parts  still  adherent,  must  be  decalcified  by  soak- 
ing for  a  long  time  in  a  i  per  cent,  solution  of  chromic  acid, 
which  should  be  frequently  changed;  it  is  then  to  be  washed 
in  distilled  water  for  twenty-four  hours,  and  hardened  in  alco- 
hol, when  it  will  be  ready  for  cutting. 

A  section  from  a  specimen  thus  prepared  shows  that  the 
whole  middle  ear  is  lined  by  a  layer  of  pavement-epithelium, 
supported  upon  two  layers  of  connective  tissue,  one  serving  as 
a  submucous  layer  and  the  other  as  a  periosteum.  This  tis- 
sue is  thrown  into  ridges  corresponding  to  the  bony  promi- 
nences, in  the  hollows  of  which  the  vessels  and  nerves  lie.  Ac- 
cording to  Kessel  the  submucous  layer  is  provided  with  oval 
expansions,  recalling  the  Pacinian  bodies  found  in  the  mesen- 
tery of  the  cat.  The  existence  of  muciparous  glands  in  the 
human  tympanum  has  yet  to  be  confirmed.  A  plex"us  of  nerves 
is  described  as  distributed  in  the  subepithelial  tissue,  in  the 
nodal  points  of  which  are  found  scattered  ganglion-cells.  The 
lining  of  the  tympanum  passes  directly  into  that  of  the  mastoid 
cells,  and  has  there  the  same  general  arrangement. 

Tlie  Eustachian  tube. — In  direct  communication  with  the 
tympanum  stands  the  Eustachian  tube,  composed  like  the  ex- 
ternal ear  of  a  cartilaginous  and  an  osseous  portion.  The  car- 


MANUAL    OF    HISTOLOGY. 

til  age,  which  gives  the  name  to  the  anterior  part  of  the  tube 
that  stands  in  connection  with  the  pharynx,  is  in  the  form  of 
a  hook  (Fig.  159,  2),  with  its  short  end  directed  downward  and 
inward.  At  the  bend  of  the  hook  the  opposing  surfaces  of  car- 
tilage cannot  quite  apply  themselves  to  each  other,  and  there 
is  thus  left  a  little  air-space  between  them,  which  Ruedinger 
has  termed  the  safety- tube  (Fig.  159,  9).  The  cartilage  is  of  the 
hyaline  variety,  with  small  cells,  which  are  much  smaller  and 
more  numerous  at  the  periphery,  thus  forming  a  sort  of  peri- 


Fio.  159.— Transverse  section  of  Eustachian  tube  and  surrounding  parts :  1,  median  cartilaginous  plate ; 
2,  lateral  cartilaginous  hook :  3,  muscnlus  dilator  tubae  ;  4,  musculus  levator  veli  palatini ;  5.  fibro-carti- 
lago  basilaris :  6  and  7,  acinous  glands ;  8,  deposit  of  fat  in  the  lateral  wall :  9,  safety-tube ;  10,  accessory 
fissure  ;  11,  fold  of  the  mucous  membrane  ;  12,  adjacent  tissues.  Ruedinger. 

chondrium.  The  cartilage  is  joined  to  the  osseous  portion  by 
a  narrow  band  of  fibro-cartilage. 

The  musculus  dilator  tubse  (Fig.  159,  3),  which  goes  to  form 
the  membranous  (muscular)  portion  of  the  tube,  is  joined  to 
the  short  end  of  the  hook  along  the  whole  length  of  the  carti- 
laginous portion.  The  muscle  is  of  the  striped  variety,  and  is 
inserted  into  the  perichondrium  by  means  of  a  very  short,  flat 
tendon. 

The  entire  tube  is  lined  with  a  mucous  membrane  (Fig.  159, 
11),  continuous  at  one  end  with  that  of  the  pharynx,  and  at  the 


THE    EAR.  357 

other  with,  that  of  the  tympanum.  This  membrane  consists  of 
several  layers  of  cylindrical  epithelial  cells,  the  upper  or  inner 
of  which  have  their  broad  surfaces  directed  inward  and  carry 
cilia.  In  the  other  layers  the  epithelia  are  wedge-shaped.  The 
epithelium  rests  upon  a  basement-membrane,  beneath  which  is 
a  layer  of  connective  tissue  (Fig.  159,  5),  in  which  lie  the  muci- 
parous  glands  (Fig.  159,  6,  7),  which  are  similar  to  those  of 
the  pharynx  and  oesophagus,  and  lined  with  wedge-shaped 
epithelium.  These  glands  are  absent  in  the  safety-tube.  A 
plexus  of  nerves  arising  from  the  pharyngeal  and  tympanic 
plexuses  has  been  demonstrated,  the  final  distribution  of  which 
to  the  glands  is  probable. 

Before  leaving  the  middle  ear  a  short  mention  of  the  os» 
sicula  and  their  mode  of  articulation  is  in  place.  The  bones 
are  composed  of  an  internal  spongy  and  an  external  compact 
portion.  The  former  is  very  rich  in  blood-vessels.  These 
bones  are  covered  in  early  life  by  the  mucous  membrane  only, 
but  in  later  life  there  is  also  a  thin  periosteum  to  be  seen. 
Their  articulation  with  each  other  is  constructed  similarly  to 
that  of  the  larger  joints;  i.e.,  their  articular  ends  are  sur- 
rounded by  a  capsule  in  which  is  a  synovial  fluid.  The  method 
of  union  of  the  foot-  plate  of  the  stapes  with  the  fenestra  ovale 
is  a  little  more  complicated.  The  bottom  and  edges  of  the  plate 
are  covered  with  a  thin  film  of  hyaline  cartilage.  The  edges  of 
the  window  are  also  covered  with  cartilage,  which  is  united  to 
that  of  the  plate  by  means  of  a  fine  network  of  elastic  tissue. 
The  base  of  the  plate  rests  upon  a  firm  connective-tissue  layer, 
a  continuation  of  the  periosteum  lining  the  inside  of  the  scala 
tympani,  and  called  the  ligamentum  baseos-stapedis. 

The  muscles  connected  with  the  ossicula  belong  to  the 
striped  variety,  and  are  connected  to  the  bones  by  tendons, 
which  are  covered  by  the  mucous  membrane  wherever  they 
pass  through  the  tympanum. 

The  internal  ear. — The  internal  ear  consists  of  two  portions, 
to  which  the  auditory  nerve  is  finally  distributed,  and  which 
are  the  essential  parts  concerned  in  the  perception  of  sound. 
These  are  the  membranous  labyrinth  and  the  cochlea. 

In  man  and  the  higher  vertebrates  both  of  these  parts  are 
enclosed  within  bony  walls,  a  circumstance  which  makes  their 
histological  study  a  matter  of  considerable  difficulty.  In  fishes, 
however,  although  the  cochlea  is  represented  merely  by  a  small 


358  MANUAL    OF    HISTOLOGY. 

diverticulum  (the  lagena),  the  membranous  labyrinth  is  fully 
developed,  and,  as  it  is  large  and  easy  of  access,  has  always 
been  a  favorite  object  for  demonstration.  Its  method  of  prep- 
aration will  be  given  here,  while  that  for  the  cochlea  will  be 
described  farther  on. 

The  membranous  labyrinth. — Our  knowledge  of  this  part 
has  been  chiefly  derived  from  studies  upon  the  pike  (esox  lu- 
cius),  perch  (perca  fluviatilis),  or  cod  (gadus  morrhua).  The 
head  is  divided  longitudinally  in  the  median  line,  and  the  brain 
carefully  removed  by  means  of  the  handle  of  a  scalpel,  when 
there  is  seen  directly  behind  the  eye  a  second  cavity  filled  with 
a  grayish  translucent  mass,  composed  principally  of  fat  and  a 
sort  of  mucous  tissue.  This  can  be  removed  with  the  aid  of 
fine  forceps,  and  there  is  usually  drawn  out  at  the  same  time 
more  or  less  of  the  semicircular  canals  with  their  ampullse  and 
the  remains  of  the  utricle  and  saccule.  With  a  little  practice, 
and  by  carefully  freeing  the  canals  from  the  short,  bony  chan- 
nels by  which  they  are  held  in  place,  the  membranous  laby- 
rinth, with  a  portion  of  the  acoustic  nerve,  can  be  removed 
entire. 

Within  the  utricle  and  saccule  are  found  the  otoliths,  con- 
cretions of  lime.  After  the  lime  has  been  removed  by  means 
of  a  weak  acid,  they  show  a  coarse,  fibrillated  structure  on 
section.  These  serve  as  a  ready  means  of  distinguishing  be- 
tween the  saccule  and  utricle,  as  the  largest  otolith  (called 
sagitta)  and  the  smallest  (asterix)  occupy  the  saccule,  the 
former  lying  on  the  expansion  of  the  acoustic  nerve  in  the  sac- 
cule proper,  while  the  latter  lies  on  the  expansion  of  the  nerve 
in  that  part  of  the  saccule  called  the  lagena,  and  which  corre- 
sponds to  the  cochlea  of  the  higher  animals.  The  medium-sized 
stone  (lapillus)  lies  upon  the  expansion  of  the  nerve  in  the  utri- 
cle. The  otoliths  are  embedded  in  a  mucilaginous  mass  lying 
directly  upon  the  termination  of  the  nerve.  In  the  higher  ani- 
mals they  are  represented  by  cretaceous  particles  in  the  macula 
acustica. 

The  labyrinth  thus  removed  is  to  be  placed,  during  twenty- 
four  hours,  in  a  1  per  cent,  solution  of  osmic  acid,  and  then 
carefully  washed  in  distilled  water.  In  order  to  obtain  the 
separate  cells,  the  point  where  the  nerve  enters  (known  by  its 
darker  color)  is  to  be  carefully  teased  with  fine  needles  and 
examined  in  glycerine.  To  obtain  good  sections,  the  por- 


THE    EAR.  359 

tions  of  the  canal  where  the  nerve  terminates,  and  the  simi- 
lar portion  of  the  saccule  and  utricle,  are  to  be  placed  for 
twenty-four  hours  in  a  saturated  solution  of  gum  arabic  in 
water,  and  then  directly  into  strong  alcohol  for  twenty-four 
hours  longer,  when  they  will  be  ready  for  embedding.  The 
sections,  made  with  a  sharp  razor,  kept  well  wet  with  alcohol, 
are  to  be  deprived  of  their  gum  by  passing  a  stream  of  distilled 
water  beneath  the  cover-glass,  the  water  being  replaced  by  a 
solution  composed  of  one  part  of  a  saturated  solution  of  ace- 
tate of  potash  and  four  parts  each  of  glycerine  and  water. 

The  structure  and  arrangement  of  the  semicircular  canals, 
except  at  the  points  of  expansion  of  the  nerve,  is  as  follows : 
In  the  osseous  fishes  the  canals  lie  embedded  in  a  mass  of  adi- 
pose tissue,  and  are  held  in  place  by  very  short  bony  tubes ; 
in  the  cartilaginous  fishes  (shark,  skate)  they  lie  in  canals  hol- 
lowed out  in  the  cartilage,  while  in  man  and  the  higher  verte- 
brates they  are  surrounded  by  bony  walls. 

In  man  the  membranous  part  does  not  entirely  fill  up  the 
bony  canals,  but  is  adherent  to  the  lining  periosteum  at  one 
point,  and  to  the  rest  of  the  wall  by  bands  of  connective  tissue 
(called  ligamentum  labyrinth!  canaliculorum  et  sacculorum),  in 
the  interstices  of  which  the  perilymph  circulates.  In  the  fishes 
the  walls  of  the  tubes  and  ampullae,  as  well  as  of  the  utricle 
and  saccule,  are  composed  of  what  has  been  termed  spindle- 
cartilage.  This  consists  of  a  homogeneous  ground-substance, 
like  that  of  ordinary  cartilage,  in  which  lie  embedded  long, 
spindle-shaped  connective-tissue  corpuscles,  anastomosing  with 
each  other  in  all  directions,  like  the  corpuscles  of  the  cornea. 
The  whole  is  lined  with  a  pavement-epithelium.  In  man  the 
structure  is  different.  Here  there  are  to  be  distinguished  three 
layers,  viz.,  externally,  a  layer  of  connective  tissue,  composed 
of  fibrous  tissue  with  numerous  nuclei.  This  is  connected  at 
one  point  with  the  periosteum,  and  passes  into  the  ligamenta 
labyrinth!  canaliculorum  at  the  other  points  of  the  circumfer- 
ence ;  secondly,  of  a  hyaline  layer,  the  tunica  propria  ;  this  is 
raised  into  papilliform  projections  in  certain  parts  of  the  tube. 
The  internal  layer  is  composed  of  simple  pavement-epithelium. 

The  distribution  and  termination  of  the  nerve  is  as  follows 
in  the  fishes:  The  acoustic  nerve  divides  into  two  branches, 
the  cochlear  and  vestibular,  each  of  which  gives  off  three  fila- 
ments. Those  from  the  cochlear  portion  supply  the  saccule, 


360 


MANUAL    OF   HISTOLOGY. 


lagena,  and  ampulla  frontalis ;  those  from  the  vestibular 
branch  go  to  the  utricle  and  the  ampullae  of  the  horizontal  and 
sagittal  semicircular  canals.  The  termination  of  the  nerves  in 
the  saccule  and  utricle  is  called  macula  acustica,  and  in  the 
ampullae,  crista  acustica. 

The  macula  is  a  small,  roundish  spot,  slightly  projecting 
above  the  surface.  Thin  sections  through  it  show  the  presence 
of  three  layers  of  cells.  Directly  upon  the  wall  proper  of  the 
canal  lies  a  single  row  of  small,  round  epithelial  cells  with 
large  nucleoli  (Fig.  160,  1).  Next  come  several  rows  of  cells  hav- 


scp.  nerxf 


cartilage. 


Pro.  160.— Section  through  the  ampulla  frontalis  of  esox  lucius:    1,  basal  cella ;  2,  cells  with  thread- 
like prolongations :  3,  cylindrical  cells,  with  cilia.     After  Kuhn. 

ing  a  round  or  oblong  (spindle-shaped)  central  portion,  from 
which  are  given  off  two  filiform  prolongations,  the  one  passing 
inward  and  standing  in  close  connection  with  a  fine  plexus  of 
nerves  lying  in  the  layer  of  round  cells  mentioned  above ;  the 
other  also  passing  inward,  but  ending  either  as  a  free  cilium 
between  the  layer  of  cells  next  to  be  described,  or  being  joined 
to  their  inner  extremity  (Fig.  160,  2,  and  Fig.  161). 

The  inner  layer  consists  of  several  rows  of  cylindrical  epi- 
thelial cells,  having  the  end,  which  is  directed  inward,  tapering 
into  a  fine  filament  connected  with  those  of  the  middle  layer,  as 


THE    EAR. 


361 


already  described.     The  free  surface  of  these  cells  is  provided 
with  numerous  hairs  (Fig.  160,  3). 

The  arrangement  of  the  cells  in  the  crista  acustica  is  essen- 
tially the  same  as  that  of  the  ma- 
cula, with  the  exception  that  the 
crista  rests  upon  an  infolding  of 
the  wall  called  the  septum  nerveum 
(Fig.  160,  sep.  nerv.),  and  has  on 
each  side  two  half  -  moon  -  shaped 
prominences  of  cylindrical  epithe- 
lium called  the  plana  semilunata 
(Fig.  160,  pi.  sem.),  into  which  no 
nerves  have  been  traced.  At  the 
point  where  the  macula  and  plana 
semilunata  pass  into  the  epithe- 
lium lining  the  rest  of  the  canal, 
there  is  found  an  intermediate  form 
of  cell,  larger  than  the  ordinary 
epithelium,  and  separated  one  from 
another  by  a  fine  web  of  connective 
tissue.  These  have  received  the 
name  of  protoplasmic  cells,  but  as 
yet  their  function  has  not  been 
discovered. 

Covering  the  crista  in  the  place 
of  an  otolith  is  a  gelatinous  mass 
in  the  form  of  a  cup,  having  a  stri- 
ated appearance,  and  into  which 
the  fine  hairs  of  the  internal  sur- 
face project.  This  is  considered  as 
a  cuticular  formation,  and  is  sup- 
posed to  act  as  a  damper  (Fig.  160, 
cupula). 

The  nerve,  after  passing  through 
the  wall  at  the  point  opposite  the 
crista  or  macula,  loses  all  its 
sheaths,  and  forms  a  fine  plexus  in 
the  outermost  layer  of  cells,  and 

this  plexus  has  been  found  to  communicate  with  the  inner 
filaments  of  the  middle  layer  of  cells,  the  internal  filaments  of 
which  ended  as  free  cilia  or  were  joined  to  cells  of  the  inner 


FIG.  161.— Separate  cells  from  the  ma- 
cula, showing  the  connection  of  the  cylin- 
drical cells  with  the  cells  having  thread- 
like processes,  and  also  the  passage  of  these 
processea  to  the  surface  between  the  cells. 
Kuhn. 


362  MANUAL    OF   HISTOLOGY. 

layer  which  were  provided  with  cilia  upon  tlieir  free  surface. 
This  can  be  best  understood  by  a  study  of  Figs.  160  and  161. 
In  man  the  arrangement,  as  well  as  can  be  followed,  is  almost 
identical  with  that  of  fishes. 

TJie  cochlea. — There  is  no  easy  method  of  obtaining  good 
preparations  of  the  cochlea,  but  that  by  which  the  best  results 
have  been  obtained  is  as  follows  :  The  portion  of  the  temporal 
bone  containing  the  internal  ear  from  a  recently  killed  animal 
(young  cat,  dog,  or  bat)  is  hardened  for  twenty-four  hours  in 
%  to  1  per  cent,  solution  of  osmic  acid  in  distilled  water, 
then  placed  in  Muller's  fluid  for  a  week,  and  decalcified  by  a 
0.01  per  cent,  solution  of  chloride  of  palladium.  After  decal- 
cification  it  is  to  be  washed  in  distilled  water  for  a  few  minutes, 
then  soaked  for  twenty-four  hours  in  a  concentrated  aqueous 
solution  of  pure  gum  arable,  and  finally  placed  directly  in 
strong  alcohol  for  twenty -four  hours.  After  this  hardening  the 
preparations  are  ready  to  be  embedded  in  soap  or  hardened 
liver,  and  cut.  The  razor  is  to  be  kept  well  wet  with  alcohol 
while  cutting.  The  sections  are  to  be  placed  directly  upon  a 
slide,  and  the  gum  removed  by  passing  a  stream  of  distilled 
water  under  the  covering-glass. 

Small  portions  of  the  lamina  spiralis  can  also  be  taken  from 
the  fresh  cochlea,  after  opening  it  carefully  with  the  bone-for- 
ceps, and  placed  in  the  vapor  of  osmic  acid  or  in  a  i  to  1  per 
cent,  solution  of  the  same  for  a  few  (twelve  to  twenty-four) 
hours.  The  preparations  thus  treated  may  be  teased  in  gly- 
cerine, and  the  separate  cells  obtained. 

The  sections  are  to  be  made  in  a  direction  parallel  with  the 
long  axis  of  the  cochlea,  and  if  the  central  shaft  (modiolus)  is 
cut  through,  the  following  picture  will  be  presented  :  On  each 
side  of  the  modiolus  are  seen  sections  of  the  canal  of  the  coch- 
lea, divided  by  a  thin  partition  (the  lamina  spiralis,  Fig.  162, 
L  sp)  into  an  upper  portion  (the  scala  vestibuli,  Fig.  162,  SV) 
and  a  lower  (the  scala  tympani,  Fig.  162,  ST).  The  scala  ves- 
tibuli is  further  subdivided  by  means  of  a  delicate  membrane, 
named  after  its  discoverer  the  membrane  of  Eeissner  (Fig.  162, 
/,  /i),  which  passes  off  at  an  angle  from  the  middle  of  the 
lamina  spiralis  and  is  inserted  into  the  wall  of  the  cochlea. 
The  portion  of  the  canal  thus  cut  off  forms  the  ductus  cochle- 
aris  (Fig.  162,  e,  et),  and  in  it  lies  the  peculiar  body  in  which 
the  nerve  terminates,  and  which  is  called  the  organ  of  Corti. 


THE   EAR. 


363 


The  scala  tympani  is  a  blind  canal,  having  at  one  extremity 
the  membrane  which  covers  the  fenestra  rotunda,  and  at  the 
upper  part  terminating  in  the  cupula  of  the  cochlea,  where  it 


s 


Lsp 


FIG.  162.— Section  of  the  cochlea  of  a  human  embryo  at  the  fourth  month,  a,  a,  a,  cartilaginous 
incasement  of  the  cochlea ;  ft.  6,  perichondrium ;  c,  mucoid  tissue  matrix  of  the  modiolus ;  d,  d,  cartila- 
ginous septa  of  the  individual  turns  of  the  cochlea ;  e — c4,  sections  of  the  ductus  cochlearis  ;  /,  f^  Reise- 
ner's  membrane  ;  #,  membrana  tectoria.  somewhat  lifted  up  from  the  subjacent  parts  ;  h.  rudiment  of  the 
stria  vascularis ;  t°,  rudiment  of  the  subsequent  organ  of  Corti ;  L  *p,  lamina  spiralis  ;  Gl,  Gl±,  ganglion 
spirale  with  various  efferent  and  afferent  bundles  of  nerves ;  /ST,  scala  tympani ;  SV,  scala  vesfibuli ; 
STlt  SVlt  /Sr2,  muccid  tissue  where  later  the  scalae  of  the  last  cochleal  turn  will  be.  10,  Waldeyer. 

is  said  to  enter  into  communication  with  the  scala  vestibuli 
by  a  minute  opening,  the  helicotrema. 

The  scala  vestibuli  stands  in  direct  communication  with  the, 
perilymphatic  space  of  the  vestibular  sacs,  while  the  ductus 
cochlearis  is  in  communication  with  the  saccule  by  means  of 
a  slender  canal  (the  canalis  reuniens).  The  walls  of  the  two 
scalse  are  formed  of  a  thin  periosteum,  on  the  surface  of  which 


364  MANUAL    OF   HISTOLOGY. 

there  can  be  shown,  by  means  of  the  silver  method,  a  layer  of 
endothelium.  This  proves  that  the  canals  are  of  the  nature  of 
serous  cavities. 

The  lamina  spiralis  is  composed  of  an  osseous  and  a  mem- 
branous portion.  The  osseous  portion  reaches  about  one-half 
the  distance  from  the  modiolus  to  the  opposite  wall,  and  on  its 
outer  and  vestibular  portion  is  a  mass  of  connective  tissue 
called  crista  spiralis  (Fig.  163,  Or.),  the  upper  lip  of  which  is 
called  labium  vestibulare  (Fig.  163,  Lv.\  while  the  lower  lip  is 
called  labium  tympanicum  (Fig.  163,  Lt.};  the  space  between  the 
two  lips  has  received  the  name  of  recessus  internus.  The  crista 
spiralis  is  divided  by  a  number  of  parallel  furrows,  which  gives 
the  surface  a  regular  toothed  appearance  when  seen  from  the 
vestibular  surface.  Hence,  the  portions  between  the  furrows 
are  called  "auditory  teeth." 

The  under  (vestibular)  of  the  two  lips  is  connected  with 
the  membrana  basilaris  (Fig.  163,  Hn,  Zp'\  which  is  com- 
posed of  two  layers  of  finely  fibrillated  connective  tissue, 
and  is  covered  on  its  tympanic  surface  by  a  layer  of  endothe- 
lium, and  on  the  surface  turned  toward  the  ductus  cochlearis 
l)y  the  organ  of  Corti  and  its  supporting  cells.  The  inner 
layer  of  this  fine  connective  tissue  is  directly  continued  into 
the  bases  of  the  pillars  of  the  organ  of  Corti  next  to  be  de- 
scribed. 

The  organ  of  Corti,  so  named  from  its  discoverer,  is  a  com- 
plicated arrangement  of  cells  in  which  the  nerve  terminates, 
and  of  other  cells  and  their  modifications,  which  apparently 
act  as  supports  to  these  and  as  modifiers  of  the  sound.  The 
cells  proper,  in  which  the  nerve  terminates,  have  received  the 
name  of  hair-cells,  from  the  ciliated  appendages  which  they 
carry  (Fig.  163,  a,  a" ,  a",  a"),  while  the  peculiar  modified  cells 
which  are  their  chief  support  are  called  the  pillars. 

The  pillars  (Fig.  163,  ft,  fa}  are  two  slender,  slightly  shaped 
bodies,  of  a  finely  fibrillated  structure,  showing,  however,  in 
their  early  stages,  the  presence  of  nuclei.  They  stand  upon 
the  membrana  basilaris,  and  are  apparently  to  be  directly  fol- 
lowed into  the  fine  layer  of  connective  tissue  beneath  them. 
They  are  arranged  in  two  rows,  named  inner  and  outer,  ac- 
eording  to  their  situation  as  regards  the  modiolus.  The  pillars 
are  inclined  toward  each  other,  and  the  space  between  them  is 
named  the  tunnel.  The  head  of  the  outer  is  a  little  enlarged 


THE    EAR. 


805 


and  rounded,  lying  in  a  shallow  depression  in  the  head  of  the 
inner  pillar,  thus  resembling  a  ball  and  socket-joint  (Fig.  163, 
gia).  The  heads  of  the  pillars,  when  seen  from  the  surface,  have 


Fio.  163.— Section  through  the  ductus  cochlearis  of  a  young  dog :  R-rf,  Reissner's  membrane ;  Los 
and  Los',  vestibular  and  tympanic  plates  of  the  osseous  lamina ;  gap,  ganglion  spirals ;  n,  fine  nerves 
passing  through  the  habenula  perforata  at  Jfn ;  Cr,  crista  spiralis ;  Lv,  its  vestibnla  or  upper  lip ; 
rm,  Mt,  m',  the  membrana  tectoria  (Corti's  membrane) ;  S#pi,  recessus  iriternus  clothed  with  epithe- 
lium ;  fl  and /a,  inner  and  outer  pillars  of  Corti ,  a  and  a",  a",  a",  inner  and  outer  hair-cells,  between 
the  latter  are  seen  the  fl^sk-shaped  cells,  r,  r,  r  ;  Tn.  nerve  passing  through  the  tunnel  to  reach  one  of 
the  outer  hair-cells  ;  Hz,  Henson's  prop-cells  :  Sp,  Zf/  zona  pectinata  ;  gia,  inner  and  outer  beads  of  the 
pillars  of  Corti :  A'p,  plate  called  phalynx.  which,  when  joined  with  its  neighbors,  forms  the  lamina  reti- 
cularis,  in  which  the  ends  of  the  hair-cells  are  supported;  Lap,  ligameutum  spirale ;  <S'w,  stria  vt 
laris.  After  Lavdowsky. 


366  MANUAL    OF    HISTOLOGY. 

prolongations  shaped  a  little  like  the  bones  of  the  fingers,  and 
hence  called  phalanges  (Fig.  163,  Kp).  These  enclose  spaces  be- 
tween them,  through  which  the  ends  of  the  hair-cells  project. 
The  network  thus  formed  is  called  the  lamina  reticularis,  and 
gives  a  very  peculiar  appearance  when  this  portion  of  the  organ 
is  viewed  from  above. 

Corresponding  to  the  pillars  are  rows  of  hair-cells  termed 
inner  and  outer — a  single  row  of  the  former  (Fig.  163,  a)  and 
four  rows  of  the  latter  (Fig.  163,  a",  a",  a").  The  shape  of 
the  cells  of  the  inner  row  is  cylindrical,  having  their  base  pro- 
longed into  a  fine  thread  expanding  into  a  foot-stalk,  which 
passes  into  the  membrana  basilaris.  The  top  of  the  cell  which 
passes  through  the  opening  in  the  lamina  reticularis  is  pro- 
vided with  fine  cilia.  The  four  rows  of  cells  in  connection  with 
the  outer  pillar  are  of  the  same  shape  as  those  of  the  inner 
row,  but,  in  addition,  are  joined  at  their  lower  part  to  peculiar 
cells  shaped  like  a  flask,  large  and  rounded  at  the  bottom,  and 
tapering  to  a  long  and  narrow  neck.  The  tops  of  these  cells 
reach  to  the  lamina  reticularis,  but  do  not  pass  through  it 
(Fig.  163,  r,  r,  r,  and  &).  Immediately  adjoining  the  outer  rows 
of  hair-cells  are  several  rows  of  cylindrical  epithelial  cells  (Hen- 
son's  prop-cells)  (Fig.  163,  Hz),  which  pass  gradually  into  the 
short  cubical  epithelium  forming  the  zona  pectinata  (Fig.  163, 
Zp  to  Zpf)  adjoining  the  epithelial  lining  of  the  ductus  cochle- 
aris. 

The  course  of  the  nerve  has  already  been  followed  to  the 
ganglion  spirale.  From  this  point  a  number  of  fine  trunks 
pass  through  a  canal  in  the  osseous  portion  of  the  lamina  spi- 
ralis  to  the  lower  lip  of  the  crista,  which  they  leave  as  naked 
axis-cylinders  by  a  number  of  small  holes,  called  the  habenula 
perforata  (Fig.  163,  Hn).  After  entering  the  ductus  cochle- 
aris  they  divide  into  two  chief  bundles,  one  distributed  to  the 
inner  hair-cells,  arid  the  other,  passing  between  the  bases  of 
the  inner  pillars,  crosses  the  tunnel  and  then  again  passes  be- 
tween the  outer  pillars,  and  terminates  finally  in  the  outer 
hair-cells.  Beyond  the  fact  that  they  apply  themselves  directly 
to  the  surface  of  the  hair-cells,  their  mode  of  ultimate  ending 
is  not  known. 

From  the  upper  edge  of  the  crista  spiralis,  lying  directly 
upon  it  and  covering  the  whole  of  the  organ  of  Corti,  is  the 
membrana  tectoria  (Corti' s  membrane)  (Fig.  163,  Mt),  a  homo- 


BIBLIOGRAPHY.  367 

geueous  mass  in  which  indistinct  striations  are  to  be  seen. 
This  is  of  the  nature  of  a  cuticular  formation,  and  probably 
acts  as  a  damper,  preventing  excessive  vibrations  of  the  organ 
of  Corti. 


BIBLIOGRAPHY. 

RUEDINGER.     The  Eustachian  Tube,  etc.     Strieker's  Histology,  New  York.     1872. 
TRAUTMANN.     Der  gelbe  Fleck  am  Ende  des  Hammergriffes.     Arch.  f.  Ohreuheilk., 

Vol.  XL,  p.  99.     1876. 
UKBANTSCHITSCH.     Zur  Anat.  d.  Gehorknochelchen  des  Menchen.     Arch.  f.  Ohren- 

heilk.,  Vol.  XL,  p.  1.     1876. 
POLITZKR.     Ueber  Anastoraosen  d.    Gefassbezirk  d.  Mittelohres  u.   d.   Labyrinths. 

Arch.  f.  Ohrenh.,  Vol.  XL,  p.  237, 1877,  and  Wien.  med.  Woch.,   No.  30.    1876. 
UEBER-LIEL.     Die  Membrana  tympani  secundaria.    Monatsschr.  f.  Ohrenheilkunde, 

No.  4.     1876. 
LAVDOWSKY.     Ueber    d.    akust.    Endapparat    d.    Saugethiere.      Arch.   f.    mikros. 

Anat.,  Vol.  XIII.,  p.  417.     1877. 
KUIIN.     Untersuch.  iiber  den  hautigen  Labyrinth  der  Knochenfische.     Arch.  f.  inikr. 

Anat.,  Vol.  XIV.,  p.  234.     1877. 
MOLDENHAUER.      Beitr.    zur.    Anat.    u.    Entwickel.    d.    Menschl.     Gehororganes. 

Arch.  f.  Ohrenheilkunde,  Vol.  XL,  p.  225.     1877. 
DORAN.     Morphology  of  the   Mammalian   Ossicula  Auditus.      Trans.    Linn.    Soc. , 

London,  Second  series,  Vol.  I.     1877. 
UEBER-LIEL.     Der  Aqueductus  cochleae  beim  Menschen.   Monatsschr.  f.  Ohrenheilk., 

Vol.  XIII.,  No.  3,  p.  33,  1878-79,  and  Virch.  Arch.,  Vol.  LXXVII.,  p.  207, 

1879;  also  Arch.  f.  Anat.  u.  Phys.,  Phys.  Abtheilung,  p.  188.     1878. 
CISOFF.     Ueber  d.  Gehorlabyrinth  d.  Knorpelfische.  Sitz.  d.  Naturf.    Gesellsch.  an 

d.  K.  Universit.  zu  Kasan.     May,  1879.     (Russian.) 
PRITCHARD.     The  Organ  of   Corti  in  Mammals.     The   Lancet,  1876,  p.  552,  and 

Proc.  Roy.  Soc.,  Vol.  XXIV.,  No.  168,  p.  346,  1878  ;  also  The  Termination  of 

the  Nerves  in  the  Vestibule  and  Semicircular  Canals  of   Mammals.      Quart. 

Journ.  Micros.  Sc.,  New  Series,  No.  64,  Vol.  XXL,  p.  398      1879. 
MINOT,  C.  S.     Recent  Investigations  of  the  Histology  of  the  Scala  Media  Cochleae. 

American  Journal  of  Otology.     April,  1881. 


PART   III. 


CHAPTER  XXII. 

THE  NASAL  FOSSAE,  PHARYNX,  AND  TONSILS. 

BY    D.    BRYSON    DELAY  AN,    M.D. 

Curator  of  the  New  York  Hospital,  New  York  City  ;   Member  of  the  American  Laryn- 

gological  Association. 

The  vestibulum  nasi  is  that  part  of  the  nasal  canal  which 
is  surrounded  by  the  anterior  cartilages  of  the  nose.  It  is  cov- 
ered by  a  continuation  of  the  exterior  skin,  which  gradually 
assumes  the  characteristics  of  a  mucous  membrane  and  pos- 
sesses several  layers  of  pavement-epithelium,  the  uppermost 
of  which  is  composed  of  horny  cells.  This  epithelium  extends 
backward  to  the  anterior  margin  of  the  inferior  turbinated 
bone  and  the  commencement  of  the  inferior  nasal  duct,  where 
it  becomes  ciliated.  The  integument  has  also  vascular  papillae, 
with  both  simple  and  compound  loops,  and  in  the  lower  part 
of  the  nose  long,  stiff  hairs  (vibrissse),  as  well  as  large  sebaceous 
follicles.  It  is  sparingly  supplied  with  blood-vessels.  The 
nerves  are  derived  from  the  trigeminus,  and  consist  of  fila- 
ments, which  probably  end  in  terminal  bulbs. 

The  respiratory  region. — The  nasal  fossae  proper,  with  the 
exception  of  a  limited  part  known  as  the  olfactory  region,  may 
be  regarded  as  a  continuation  of  the  respiratory  tract.  Each 
fossa  communicates  with  four  sinuses :  the  frontal,  the  sphe- 
noidal,  the  maxillary  or  antrum  Highmorianum,  and  the  pos- 
terior ethmoidal.  The  mucous  membrane  covering  the  respira- 
tory region  and  its  accessory  sinuses  is  called  the  Schneiderian 
or  pituitary  membrane.  It  is  devoid  of  papillae,  and  is  covered 
with  a  cylindrical  ciliated  epithelium,  like  that  of  the  trachea, 


THE    NASAL    FOSSAE,    PHARYNX,    AND    TONSILS.  369 

the  ciliary  current  being  invariably  toward  the  choanse  (poste- 
rior nares).  It  contains,  also,  goblet-cells.  Under  the  epithe- 
lium is  a  true  membrana  mucosa,  which  forms  at  the  same 
time  a  periosteum  for  the  bones,  and  is  composed  almost  en- 
tirely of  connective  tissue,  scantily  permeated,  if  at  all,  with 
elastic  tissue-elements.  The  mucous  membrane  may  be  divided 
into  two  varieties :  a  thinner  membrane,  covering  the  internal 
surface  of  the  turbinated  bones  and  the  accessory  sinuses,  and 
the  thicker  membrane  of  the  nasal  fossse  proper. 

The  thinner  membrane  contains  many  acinous  glands.  In 
the  adjacent  cavities  they  are  less  abundant,  excepting  upon 
the  internal  wall  of  the  maxillary  sinus.  Here,  and  in  the 
s'phenoidal  sinus,  the  glands  consist  of  several  cylindrical 
tubes  with  connecting  single  oblong  acini.  The  epithelium  of 
the  latter  is  pyriform,  while  in  the  tubes  it  is  cylindrical.  The 
mucous  membrane  itself  is  pale  in  color,  and  scantily  supplied 
with  blood-vessels.  Special  nerve- terminations  have  been  de- 
scribed in  these  sinuses.  These  are  probably  nothing  more 
than  terminations  of  fibres  from  the  great  sympathetic,  having 
at  their  extremities  ganglionic  cellules. 

The  thicker  membrane  covers  the  lower  part  of  the  nasal 
septum  and  the  inferior  and  middle  turbinated  bones.  It  is 
lined  with  the  same  ciliated  epithelium,  and  in  the  anterior 
two- thirds  of  the  turbinated  bones  forms  only  a  delicate, 
slightly  corrugated  covering  for  the  subjacent  parts.  Poste- 
riorly, however,  its  surface  is  thrown  into  numerous  thick 
folds,  evidently  designed  to  increase  the  extent  of  surface  of 
the  mucous  membrane. 

The  membrana  mucosa  forms  a  fibrous  network,  which 
passes  between  the  glands  and  vessels  and  connects  the  mu- 
cous membrane  with  the  periosteum.  Its  characteristics  re- 
semble more  nearly  those  of  periosteum,  so  that  it  may  properly 
be  classed  as  a  part  of  the  latter.  The  glands  of  this  region 
vary  somewhat  from  the  acinous  type,  and  are  composed  of 
tortuous  tubules,  having  many  sinuses  and  oblong  offshoots. 
They  are  lined  on  their  inner  surface  with  low  cylindrical  epi- 
thelium, and  sometimes  assume  a  circular,  sometimes  an  oval 
or  tubular  shape  in  the  microscopic  section.  The  thickness  of 
the  pituitary  mucous  membrane  is  due  not  only  to  its  mucous 
glands,  but  more  particularly  to  the  existence  in  it  of  true  erec- 
tile tissue,  as  well  as  venous  plexuses.  (See  p.  160).  These  are 
24 


370  MANUAL   OF   HISTOLOGY. 

most  abundant  at  the  posterior  extremity  of  the  inferior  tur- 
binated  bones.  Some  of  these  vessels  are  prolonged  throughout 
the  continuity  of  the  bone  on  the  lateral  as  well  as  the  median 
side,  to  appear  with  greater  frequency  at  the  anterior  extrem- 
ity, without,  however,  regaining  the  number  or  size  which  they 
possessed  at  their  origin.  Where  they  are  less  numerous  the 
remaining  space  is  almost  entirely  occupied  by  ]arge  mucous 
glands. 

In  the  bony  framework  of  the  inferior  turbinated  bone,  large, 
bright  interspaces  are  seen  in  the  fine  trabecular  substance, 
which  are  filled  with  fibrous  tissue  containing  pale  lymphoid 
cells.  In  this  fibrous  tissue  are  usually  found  transverse  sec- 
tions of  delicate  vessels,  the  walls  of  which  are  apparently 
composed  of  fibrous  tissue.  In  order  to  reach  the  outer  sur- 
face these  vessels  either  perforate  the  bone  or  lie  in  recesses 
separated  from  the  soft  parts  only  by  the  periosteum.  In  the 
middle  three-fifths  of  the  bone,  where  the  osseous  structure 
contains  the  largest  cavities,  we  find  in  the  vicinity  of  the  ves- 
sels large,  round,  and  polygonal,  glistening  cells,  analogous  to 
marrow-cells.  A  recent  author  believes  most  of  the  above- 
mentioned  vessels  to  be  lymphatics.  The  arteries  of  the  infe- 
rior turbinated  bone  do  not  number  more  than  three  or  four, 
and  are  derived  from  the  posterior  nasal  artery. 

The  olfactory  region  is  situated  in  the  uppermost  portion 
of  the  nasal  cavity.  Its  inferior  limit  in  man  has  not  yet  been 
accurately  determined.  According  to  the  generally  received 
views  of  Schultze  and  Ecker,  it  is  probably  limited  to  the  roof 
of  the  nasal  fossae,  the  superior  turbinated  bone,  and  the  cor- 
responding part  of  the  septum.  The  mucous  membrane  of  this 
region  is  of  a  dull,  yellowish  brown  color,  and  is  perceptibly 
thicker  and  softer  than  that  of  the  respiratory  region.  This 
color  proceeds  from  fine  pigment-molecules,  which  are  em- 
bedded partly  in  the  bodies  of  the  cylindrical  epithelial  cells, 
and  partly  in  the  cells  of  an  especial  gland-formation  found 
here.  Soon  after  death,  however,  it  becomes  unrecognizable. 
Under  the  microscope  the  olfactory  region  is  seen  to  be  bound- 
ed by  a  tolerably  well-defined,  serrated  border,  although  isl- 
ands of  ciliated  epithelium,  such  as  is  found  in  the  respira- 
tory region,  are  frequently  found  scattered  about  in  different 
parts  of  it.  The  differences  of  structure  in  the  olfactory  mu- 
cous membrane  depend  upon  the  character  of  the  epithelium, 


THE    NASAL    FOSSAE,    PHARYNX,    AND    TONSILS.  371 

the  occurrence  of  peculiarly  constructed  glands — Bowman's 
glands — and  upon  the  relations  of  the  nerves. 

The  fundamental  layer  of  the  mucous  membrane  is  com- 
posed of  a  finely  fibrillated  connective  tissue,  rich  in  cells,  the 
arrangement  of  which  is  determined  by  the  numerously  dis- 
tributed glands,  nerves,  and  vessels  which  it  contains.  As  in 
the  other  regions  of  the  nasal  cavity,  the  mucosa  seems  to  pass, 
without  a  well-defined  limit,  into  the  periosteum.  In  many 
places  aggregations  of  small  pigmented  nuclei  are  found,  some 
in  the  shape  of  long  strips  lying  near  the  nerve-branches,  some 
in  other  situations,  in  rounded  or  irregular  groups. 

The  olfactory  epithelium  attains  a  considerable  thickness. 
It  consists  of  a  single  layer  of  very  elongated  cells,  which 
Schultze  has  proved  to  be  of  two  kinds,  epithelial  cells  and 
olfactory  cells. 

The  olfactory  cells  are  slender,  delicate  structures,  in  which 
may  be  distinguished  a  cell-body  and  two  prolongations  going 
in  opposite  directions — the  one  to  the  periphery,  the  other  cen- 
trally. The  bodies  of  the  olfactory  cells  are  not  all  located  in 
the  same  plane  of  the  epithelial  stratum.  The  majority,  how- 
ever, occupy  its  deeper  portions.  The  cell-body  appears  spin- 
dle-shaped or  pyriform.  It  is  finely  granulated,  and  has  in  its 
central  and  widest  portion  a  spherical,  light-colored,  ill-de- 
fined nucleus.  The  peripheral  prolongation  is  generally  rod- 
shaped,  but  now  and  then  presents  slight  sinuosities.  It  is 
sharply  outlined  and  homogeneous,  and  its  free  extremity,  in 
some  animals  (amphibia  and  birds),  has  a  tuft  of  the  most  deli- 
cate hairs,  which  project  above  the  surface  of  the  epithelium. 
In  man  this  is  not  the  case.  The  opposite  prolongation  is  ex- 
tremely delicate  and  perishable,  and,  by  some  methods  of 
preparation,  resembles  the  finest  nerve-fibrils,  sometimes  cov- 
ered with  varicosities,  at  others  entirely  smooth.  It  runs  con- 
tinuously and  undivided  as  far  as  the  base  of  the  epithelial 
stratum,  where  it  appears  to  meet  the  final  radiations  of  the 
olfactory  nerve,  partly  intertwines  with  these  radiations,  and 
then  escapes  further  investigation. 

The  indifferent  epithelial  cells  appear  in  the  form  of  an 
elongated  cylinder  with  a  very  fine,  granulated  cell-body  and 
an  ellipsoid  nucleus.  Near  the  latter  the  cell  suddenly  con- 
tracts into  a  slender,  very  pale,  centrally  directed  prolongation, 
the  inferior  end  of  which  becomes  somewhat  wider,  and 


372  MANUAL    OF    HISTOLOGY. 

brandies  into  a  number  of  delicate  filaments,  by  means  of 
which  the  cell  is  attached  to  the  fundamental  layer  of  connec- 
tive tissue.  These  widened  extremities  of  the  cells  often  con- 
tain a  brownish,  partly  nuclear,  partly  diffused  pigment. 
Viewed  upon  the  plane  surface,  the  number  of  olfactory  cells 
is  apparently  larger  than  that  of  the  cylindrical  cells.  Each 
one  of  the  latter,  however,  is  generally  surrounded  by  six  of 
the  olfactory  cells,  which  completely  fill  the  intermediary 
spaces  between  the  cylindrical  bodies.  Both  varieties  of  cells 
are  so  accurately  adjusted  to  each  other  that,  especially  in  the 
wider  portion  of  the  epithelial  cells,  fine  longitudinal  furrows 
may  be  seen,  into  which  the  peripheral  continuations  of  the 
olfactory  cells  have  been  received. 

The  surface  of  the  epithelium  is  covered  by  a  delicate  mem- 
brane, discovered  by  Yon  Brunn,  and  called  by  him  the  mem- 
brana  limitans  olfactoria.  He  has  compared  it  to  the  membrana 
limitans  externa  of  the  retina,  and  describes  its  free  surface  as 
being  plane  and  even,  while  its  lower  surface  covers  completely 
the  rounded  terminations  of  the  epithelial  cells.  The  periph- 
eral prolongations  of  the  olfactory  cells  pass  through  this 
membrane,  and  terminate  with  bare  extremities  at  the  level  of 
its  free  plane. 

The  olfactory  nerves. — The  branches  from  the  olfactory 
ganglia  which  emerge  through  the  apertures  of  the  lamina  cri- 
brosa  are  composed  entirely  of  non-medullated  filaments,  which 
resemble  embryonic  nerve-fibres.  They  next  anastomose  in  the 
deeper  layers  of  the  mucous  membrane,  and  form  a  dense 
plexiform  mesh  work,  which  sends  fine  branches  toward  the 
surface.  In  these  branches  the  axis-cylinders  are  broken  up 
into  numerous,  very  fine,  varicose  fibrils,  which  ascend  to  the 
limit  of  the  epithelial  layer,  where  they  are  lost.  Most  au- 
thors agree  with  Schultze  that  there  is  a  distinct  connection 
between  the  nerve-fibrils  and  the  olfactory  cells.  Exner  be- 
lieves that  the  nerve-fibrils  connect  with  the  epithelial  cells 
also.  He  argues,  moreover,  that  intermediary  forms,  between 
the  two  varieties  of  epithelium,  are  found,  which  would  prove 
that  they  are  not  different  structures,  but  one  and  the  same. 
Neither  of  these  views  has  yet  been  established. 

Bowman^  s  glands,  peculiar  to  the  olfactory  mucous  mem- 
brane, are  found  in  it  in  large  numbers.  They  occupy  almost 
the  whole  thickness  of  the  mucous  membrane,  their  bodies  be- 


THE    NASAL    FOSSAE,    PHARYNX,    AND    TONSILS.  373 

ing  located  in  the  deeper  layers  of  the  connective  tissue.  In 
man  their  shape  varies  somewhat  from  that  of  simple  tubules, 
as  several  glandular  tubes  ordinarily  unite  in  a  common  excre- 
tory duct,  so  that,  in  some  cases,  the  gland  almost  appeai-s 
racemose.  The  glandular  cells  are  partly  round,  partly  irreg- 
ular in  shape,  and  have  many  pale  nuclei,  together  with  a 
brownish-colored  pigment. 


THE   PHARYNX. 

The  mucous  membrane  of  the  pharynx  is,  in  general,  simi- 
lar to  that  of  the  mouth.  It  consists  essentially  of  a  stratified 
pavement-epithelium,  a  rather  loosely  woven  submucosa,  which 
contains  aggregations  of  mucous  glandules,  and  a  tunica  pro- 
pria  composed  of  fibrillary  connective  tissue  and  furnished 
with  papillae.  The  papillae  are  smaller  than  those  found  lower 
down  in  the  oasophagus.  The  mucous  glandules  are  most 
abundant  in  the  superior  part  of  the  pharynx.  The  mucous 
membrane  of  the  vault  of  the  pharynx,  and  in  the  vicinity  of 
the  isthmus  of  the  fauces,  where  it  becomes  continuous  with  the 
mucous  membrane  of  the  nasal  cavity,  to  some  extent  assumes 
the  characteristics  of  the  latter.  In  this  region  the  connective 
tissue  is  more  or  less  thickly  interspersed  with  lymphoid  cells. 
It  is  provided,  moreover,  with  ciliated  cylindrical  epithelium. 
In  adults  this  epithelium  extends  some  distance  backward  until 
it  passes  into  the  stratified  pavement  variety.  In  children, 
however,  ciliated  epithelium  lines  the  whole  naso-pharynx. 
In  the  upper  and  lateral  parts  of  the  pharynx  are  found  cer- 
tain aggregations  of  adenoid  tissue,  most  abundantly  in  the 
vault  of  the  pharynx,  extending  from  one  Eustachian  tube  to 
the  other.  This  tissue  is  generally  quite  diffuse,  but  is  identi- 
cal in  its  structure  with  the  lingual  follicular  glands  arid  with 
the  tonsils,  and  from  this  resemblance  it  has  derived  the  name 
"pharyngeal  tonsil." 

THE  TONSILS. 

The  tonsil  consists  essentially  of  a  reduplication,  more  or 
less  extensive,  of  the  oral  mucous  membrane,  containing  in  its 
folds  an  abundance  of  the  so-called  adenoid  tissue. 


374  MANUAL    OF   HISTOLOGY. 

Its  gross  structure  varies  in  different  animals.  In  some  the 
organ  is  entirely  absent.  Its  simplest  form  is  found  in  the  rab- 
bit, where  it  resembles  a  large  lingual  f ollicular  gland.  In  man 
its  usual  shape  is  ovoid.  Its  average  vertical  diameter  is  20 
mm.,  and  its  transverse  diameter  13  mm.  Its  surface  is  per- 
forated by  a  varying  number  of  slit-like  and  circular  depres- 
sions, the  common  orifices  of  the  system  of  cavities  which  it 
contains.  If  the  tonsil  of  the  rabbit  be  considered  a  single 
follicular  gland,  we  have  in  man  a  multiplication  of  this  to  the 
number  of  from  eight  to  eighteen,  the  interval  between  each 
gland  forming  a  "  lacuna  tonsillaris,"  crypt,  or  one  of  the  sys- 
tem of  cavities  mentioned  above.  There  are  also  in  the  interior 
of  the  tonsil  single  larger  cavities,  each  of  which  includes  sev- 
eral follicular  folds  and  procures  their  common  discharge  at 
the  periphery.  The  crypts  generally  are  filled,  more  or  less, 
with  a  yellowish  substance  composed  of  fat-molecules,  detached 
pavement-epithelium,  lymph-corpuscles,  small  molecular  gran- 
ules, and  cholesterin- crystals,  which  probably  proceed  from 
retained  and  decomposed  epithelial  matter,  and  perhaps  now 
and  then  from  the  bursting  of  follicles  whose  cells  have  in- 
creased by  proliferation  and  have  undergone  retrograde  meta- 
morphosis and  fatty  degeneration.  In  its  minute  anatomy  the 
tonsil  is  for  the  most  part  like  other  so-called  adenoid  glands. 
In  common  with  the  rest  of  the  oral  cavity,  it  is  invested  with 
a  thick  covering  of  pavement-epithelium,  which  rests  upon  a 
delicate  endothelioid  basement-membrane.  Following  this  is  a 
tolerably  compact  mucosa,  formed  of  interlacing  bands  of 
fibrous  connective  tissue  and  containing  many  connective-tis- 
sue corpuscles.  In  the  normal  adult  tonsil  this  structure  is  so 
delicate  that  sometimes  it  is  hardly  recognizable.  From  it 
bands  of  connective  tissue  extend  centrally  into  the  larger  ton- 
sillary  folds,  and  the  whole  forms  essentially  both  an  enclosure 
and  a  framework  for  the  adenoid  tissue  or  proper  substance  of 
the  gland,  as  well  as  a  nidus  for  its  vessels.  The  minute  struc- 
ture of  the  adenoid  tissue  of  the  tonsil  does  not  differ  from 
that  of  other  follicular  glands  (those  of  the  intestine,  etc.),  de- 
scribed elsewhere.  Occasionally,  in  the  tonsil  the  adenoid  tis- 
sue extends  so  near  the  periphery  as  to  penetrate  the  mucosa 
and  encroach  upon  the  epithelial  layers.  This  is  especially 
the  case  in  the  walls  of  the  crypts,  where  the  epithelium  com- 
monly exists  in  a  modified  form,  or  is  altogether  wanting.  The 


BIBLIOGRAPHY.  375 

tonsil  is  supplied  abundantly  with  racemose  mucous  glands, 
which  are  most  numerous  in  the  neighborhood  of  the  hilus. 
Here,  also,  may  be  found  small  bundles  of  muscular  fibres 
apparently  independent. 


BIBLIOGRAPHY. 

KOLLIKER.     Ueber  das  Geruchsorgan  von  Amphioxus.     Miiller's  Archiv  fur  Anat. 

und  Physiol.     1843. 

KOHLRAUSCH.     J.  Miiller's  Archiv,  pp.  8,  149.     1853. 
ECKER.     In   Berichte    iiber    die  Verhandlungen  zur  Beforderung  der  Naturwiss. 

No.  12.     Fribourg,  1855. 
SCHULZE,  MAX.     Ueber  die  Endigungsweise  der  Geruchsnerven  und  die  Epithelial- 

gebilde  der  Nasenschleimhaut.      Monataberichte  der  konigl.  Acad.  der  Wis- 

sensch.     Berlin,  1856. 
ECKER.     Ueber  die  Geruchsscbleimhaut  des  Menschen.    Zeitschrift  f .  wiss.  Zoologie. 

VIII.,  p.  305.     1856. 
ECKER,  A.     Bericht  iiber  die  Fortschritte,  Anafcomie  und   Physiologic   f.  d.  Jahr 

1856,  p.  117.     Von  Henle  und  Meissner. 

TODD  and  BOWMAN.     The  Physiological  Anatomy  of  Man.     II.     London,  1856. 
SEEBERG.     Disquisitionea  Microscopicae  de  textura  membranae  pituitaria3  nasi.    Diss. 

Inaug.     Dorpati,  1856. 
KOLLIKER.     Ausbreitung  der  Nerven  in  der  Geruchsschleimhaut  von  Plagiostomen. 

Sitzber.  der  physik.-med.  Gesellschaft,  T.  VIII. ,  pp.  31.     Wurtzburg,  1857. 
ERICHSEN.     De  textura  nervi  olfactorii  ejusque  ramorum.      Th.  inaug.      Dorpat, 

1857. 

HOYER.     De  tunicse  mucosaa  narium  structura.     Berolini,  1857. 
ECKHARDT.     Ueber  Endigungsweise   der   Geruchsnerven.      Beitrag  zur  Anatomie 

und  Physiologie.     4.  Abhand.,  p.  97.     1858. 
GASTALDI.     Nuovi  Ricerche  sopra  la  terminazione  del  nervo  olfactorio,  in  memorie 

de  1'Acad.  reale  della  Scienza  de  Torino.     XVII.,  p.  372.     1858. 
FUNKE,  O.     Lehrbuch  der  Physiologie.     2.  Auflage.     1858. 
KOLLIKER.     Handbuch  der  Gewebelehre.     3.  Auflage,  p.  680.    1859. 
HOYER.    Ueber  die  mikroskopischen  Verhaltnisse  der  Nasenschleimhaut.    In  Miiller'a 

Archiv  f.  Anat.  und  Physiolog.,  1861,  p.  287  ;  1860,  p.  6. 

CLARKE,  LOCKHART.     Ueber  den  Bau  des  Bulbus  olfactorius  und  der  Geruchs- 
schleimhaut.    Zeitsch.  f.  wissens.  Zoologie.     XI.     1862. 
WALTER,  G.     Ueber  den  feineren  Bau  des  Bulbus  olfactorius.    Virchow's  Arch.,  T. 

XXII.,  p.  261.     1862. 

HENLE.     Handbuch  der  systematischen  Anatomie  des  Menschen.     Bd.  II.     Braun- 
schweig, 1866. 
ZERNOFF.     Ueber  das  Geruchsorgan  der  Cephalopodon.     Bull,  de  la  Soc.  imp.  des 

sc.  nat.  de  Moscow.     2e  serie.     XLII.     1869. 
EXNER.     Weitere  Studien  iiber  die  Structur  der  Riechschleimhaut  bei  Wirbelthie- 

ren.     Sitzungsberichte  der  k.  Akad.  der  Wissenschaften.     Wien.     Band  LXV. 

3.  Abth.     1872.     Et  Bd.  LIII.     1867-1869. 


376  MANUAL    OF   HISTOLOGY. 

HEIDENHAIN,  A.     Ueber  die  acinosen  Driisen  der  Schleimhaute,  ins  besondere  der 

Nasenschleimhaut.     Diss.  Inaug.     Breslau,  1870. 
SCHULZE,  MAX.     Untersuchungen  iiber  den  Bau  der  Nasenschleimhaut.    InAbhand- 

lung.  d.  naturforsch.  Gesellschaft.     VII.     HaUe,  1872. 
BABUCHLN.     Das  Geruchsorgan.     In  Strieker's  Handbuch.     1872. 
MARTIN.     Studies  from  the  Physiol.  Lab.  in  the  University  of  Cambridge.    I.    1873. 
CISOFF.     Zur  Kenntniss  der  Regio  Olfactoria.     Centralblatt.     1874. 
BIGELOW,  H.  J.     On  the  Anat.  of  the  Turbinated  Corpora  Cavernosa.    Boston,  Med. 

and  Surg.  Journal.     April,  25,  1875. 
SHOFJELD,  B.  N.  A.     Taste-Goblets  in  the  Epiglottis  of  the  Dog  and  Cat.     Journal 

of  Anat.  and  Physiol.     X.,  p.  475.     1876. 

H5NIGSCHMIED.     Ztschr.  f.  wiss.  Zool.      XXIX.,  S.  255.     1877. 
DAVIS,  C.     Die  becherf ormigen  Organe  des  Kehlkopf es.     Arch,  f .  mikroskop.  Anat. , 

XTV.,  S.  158.     1877. 
PODWISOTZKY.     Anatomische  Untersuchungen  iiber  die  Zungendriisen  des  Menschen 

und  der  Saugethiere.     Inaugural  Dissertation.     Dorpat,  1878. 
LOWE.     Beitrage  zur  Anatomic  der  Nase  und  Mundhohle.     S.  20.    Berlin,  1878. 
ZUCKERKANDL.     Ueber  die  norm,  med.-path.  Anat.  der  Nasen-  und  angrenzenden 

Hohlen.     All  Wien.  med.  Ztg.,  No.  51.     1879. 
STEINBRUGGE,  H.     The  Histology  of  the  Inferior  Turbinated  Bones  and  of  the  Tele- 

angiectatic  Fibromata  Arising  from  These.     Archives  of  Otology,  New  York, 

Oct.,  1879. 


CHAPTER  XXIII. 

THE  MOUTH  AND  TONGUE. 

BY   D.    BRYSON    DELAY  AN,    M.D. 

Curator  of  the  New  York  Hospital,  New  York  City ;   Member  of  the  American  Laryn- 

gological  Association. 

WITH  the  exception  of  a  few  remarkable  modifications,  the 
structure  of  the  mucous  membrane  of  the  buccal  cavity  is  the 
same  throughout. 

The  tunica  propria  consists  of  fibrillated  connective  tissue, 
made  up  of  tolerably  minute  bundles  of  intertwining  filaments. 
Between  these  appear  many  delicate,  elastic  fibres.  Toward 
the  epithelium  this  structure  becomes  less  distinct,  and  an  ex- 
ceedingly delicate,  filamentous  network  is  developed.  The  con- 
nective-tissue cells  with  their  nuclei,  on  the  other  hand,  become 
more  marked.  The  surface  of  the  tunica  propria  contains 
many  slender  papillae,  which  penetrate  more  or  less  deeply 
into  the  epithelial  covering.  They  have,  also,  the  above-men- 
tioned filamentous  structure,  but  contain  few  cellular  elements. 

The  transition  of  the  tunica  propria  into  submucous  connec- 
tive tissue  is,  in  general,  hardly  perceptible.  The  latter,  how- 
ever, contains  fewer  elastic  filaments  and  broader  bundles  of 
connective  tissue.  The  epithelium  lining  the  buccal  cavity  is, 
throughout,  stratified  pavement.  The  mucous  membrane  of 
the  mouth  varies  in  different  regions  as  to  the  thickness  of  its 
different  strata,  the  height  of  its  papillae,  and  the  condition  of 
the  submucous  tissue.  It  is  thickest  and  firmest  in  the  gums 
and  near  the  palate — particularly  in  the  posterior  section  of  the 
hard  palate — and  thinnest  in  its  reduplications,  e.g.,  the  froe- 
num  linguae,  glosso-epiglottic  fold,  and  the  pillars  of  the  fau- 
ces. Its  firmness  in  the  above  places  is  due  to  the  density  of 
the  submucosa,  which  forms,  with  the  underlying  periosteum, 
one  compact  mass  of  connective  tissue. 


378  MANUAL    OF    HISTOLOGY. 

Elsewhere  the  mucosa  is  looser,  so  that  the  mucous  mem- 
brane is  readily  thrown  into  folds.  It  is  thickest  wherever  ifc 
has  intervening  layers  of  glands.  In  some  places,  especially 
in  the  lips  and  soft  palate,  the  submucosa  is  crossed  by  bun- 
dles of  striped  muscular  fibres,  which  are  connected  partly 
with  the  submucosa,  and  partly  with  the  tunica  propria.  The 
papillcz  of  the  mucous  membrane  are  most  developed  at  the 
margin  of  the  lip  and  its  immediate  vicinity,  as  well  as  on  the 
gums,  attaining  here  a  height  of  0.5  mm.,  and  often  termina- 
ting in  a  double  point.  In  the  reduplications  of  the  mucous 
membrane  (the  fraenum  linguae,  etc.),  and  partly  in  the  region 
of  the  hard  palate,  the  papillae  are  very  small,  sometimes  rudi- 
mentary. The  thickness  of  the  epithelial  layer  is  proportion- 
ate to  the  height  of  the  papillae.  Beginning  at  the  vermilion 
border  of  the  lips,  and  going  backward,  the  epithelial  cov- 
ering becomes  progressively  thicker,  and  is  thickest  at  the 
posterior  margin  of  the  lip,  decreasing  rapidly  on  the  pos- 
terior surface.  Upon  the  cheeks  and  on  the  anterior  surface 
of  the  hard  palate  the  epithelium  is  of  medium  thickness ; 
it  is  thinnest  on  the  floor  of  the  mouth  and  on  the  above- 
mentioned  reduplications.  There  are,  however,  deviations  in 
these  proportions,  especially  in  the  hard  palate,  where  the 
papillae  are  in  some  cases  absent.  Moreover,  the  tunica  pro- 
pria sometimes  assumes  an  almost  tendinous  character.  Cer- 
tain important  aggregations  of  glands,  the  so-called  raucous 
glandules,  are  found  lodged  in  the  submucous  connective  tis- 
sue of  the  mouth.  These  are  the  labial,  buccal,  palatal,  and 
molar  glandules.  They  are  found  as  white,  sharply  denned 
knobs,  visible  to  the  naked  eye  upon  the  posterior  surface  of 
the  lips,  as  well  as  upon  the  cheeks,  palate,  and  bottom  of  the 
buccal  cavity.  In  some  cases  they  are  aggregated  into  a  few 
large  clusters,  while  in  others  they  are  more  scattered  and 
smaller.  The  orifices  of  their  ducts  are  best  seen  in  the  lining 
membrane  by  everting  the  lips  or  cheek.  They  belong  to  the 
acinous  type,  and  have  a  short  duct,  generally  somewhat 
curved,  relatively  wide,  but  somewhat  contracted  at  the  ori- 
fice. The  greatest  width  of  the  tubes  is  at  their  place  of  seg- 
mentation. On  the  branches  themselves  are  smaller  ramifica- 
tions, which  either  terminate  directly  with  globular  or  ellipsoid 
alveoli,  or  previously  divide  into  one  or  more  twigs.  It  often 
happens  that  a  small  group  of  acini,  with  a  narrow  common 


THE    MOUTH    AND    TONGUE.  379 

duct,  situated  near  a  larger  duct,  discharge  into  the  latter  near 
the  surface  of  the  mucous  membrane,  appearing  like  a  small 
accessory  glandule.  The  walls  of  the  glandules  consist  of  a 
structureless  basement-membrane,  upon  the  interior  surface  of 
which  are  superimposed  cylindrical,  clear,  almost  homogene- 
ous-looking cells,  with  oblong  nuclei. 

As  for  the  connection  of  the  buccal  mucous  membrane  with 
the  underlying  structures,  different  conditions  obtain  in  differ- 
ent regions.  Its  connection  with  the  hard  palate  and  gums 
has  been  described  above.  Where  it  is  superimposed  upon  a 
yliarply  defined  muscle,  e.g.,  over  the  floor  of  the  mouth,  and 
over  the  sublingual  gland,  it  passes  into  the  connective- tissue 
sheath  of  the  part. 

The  blood-vessels  of  the  mucous  membrane  are  arranged  in 
two  systems  of  superficially  extended  networks.  The  deeper 
one,  located  in  the  submucosa,  is  composed  of  the  mutually 
anastomosing  branches  of  the  afferent  and  efferent  vessels. 
From  this  network  many  smaller  vessels  penetrate  into  the 
tunica  propria,  which,  by  division  into  still  smaller  branches, 
and  by  frequent  anastomoses  with  one  another,  form  the  more 
superficial  and  finer-meshed  vascular  net.  In  both  nets  the 
venous  and  arterial  branches  run  tolerably  parallel.  From  the 
superficial  network  very  fine  branches  enter  the  papillae,  where, 
according  to  their  size,  they  form  either  capillary  nets  or  sim- 
ple loops. 

The  lymphatics  form  wide  networks  in  the  submucosa, 
and  narrow  nets  in  the  tunica  propria.  Single  small  vessels 
cross  those  of  the  vascular  nets.  That  lymphatics  pene- 
trate the  papilla?  is  doubtful.  The  nerves  of  the  buccal  mu- 
cous membrane  form  in  the  submucosa  more  or  less  dense 
plexuses,  in  which  many  separations  of  the  single  nerve-fibrils 
may  be  noticed.  Thence  numerous  filaments,  partly  isolated, 
partly  arranged  in  small  bundles,  and  always  medullated, 
ramify,  and  radiate  in  wider  ramifications  toward  the  super- 
ficial layers  of  the  mucous  membrane.  A  certain  number 
of  nerve-fibrils  approach,  the  papillae,  to  implant  themselves 
either  at  their  bases  or  at  the  centre  of  their  apices,  some- 
times even  at  their  extremities,  in  the  terminal  bulbs  of 
Krause.  Such  fibrils  are  most  abundant  in  the  lips  and  in  the 
anterior  surface  of  the  velum  palati,  and  in  smaller  quantity  in 
the  cheek  and  bottom  of  the  mouth.  Nerve-fibrils  may  some- 


380  MANUAL    OF    HISTOLOGY. 

times  be  seen  also  with  double  contours,  which  wind,  during 
their  course,  into  a  coil  in  the  superficial  layers  of  the  mucous 
membrane. 


THE   TONGUE. 

Although  the  mucous  membrane  of  the  tongue  is,  in  the 
general  details  of  its  construction,  similar  to  that  of  the  rest  of 
the  buccal  cavity,  it  nevertheless  presents  some  striking  pecu- 
liarities, mainly  due  to  the  configuration  of  its  upper  surface. 
This  is  covered  by  many  closely  aggregated  prominences  of 
the  mucous  membrane — the  lingual  papillce — which  give  it  a 
roughened,  fungoid  appearance.  Upon  the  under  surface  of 
the  tongue  the  papillae  are  absent,  but  the  mucous  membrane 
here  contains  a  large  number  of  follicular  glands.  The  lateral 
edges  of  the  tongue  are  here  and  there  covered  with  lingual  pa- 
pillae, which  are  often  arranged  in  rows,  and  toward  the  base 
of  the  tongue  are  replaced  by  the  so-called  fimbrice  linguce. 
Besides  simple  papillae,  analogous  to  those  of  the  skin,  the  lin- 
gual mucosa  is  studded  with  three  distinct  varieties  of  com- 
pound papillae — the  filiform,  the  fungiform,  and  the  circum- 
vallate.  These  are  distinguished  from  the  ordinary  papillae  of 
the  mucous  membrane,  not  only  by  their  large  size  and  their 
peculiar  shapes,  but  also  by  their  complicated  structure,  by  the 
arrangement  of  their  secondary  papillae,  and  the  conditions  of 
their  epithelial  coverings.  Between  these  three  forms  are 
several  intermediary  ones.  The  filiform  papillce  are  found  all 
over  the  dorsum  of  the  tongue,  anterior  to  the  line  of  the  cir- 
cumvallate  papillae.  Not  only  in  different  individuals,  but 
also  in  the  same  tongue,  there  are  marked  variations  in  their 
form.  At  the  tip  and  lateral  edges  of  the  tongue  they  are 
always  smaller,  and  their  filaments  are  wanting  or  merely  ru- 
dimentary. Toward  the  centre  of  the  tongue  they  gradually 
become  larger  and  more  abundant,  and  attain  their  highest 
development  in  the  angle  made  by  the  circumvallate  papillae. 

Their  shape  is  that  of  a  truncated  cone,  which  has  at  its 
free  extremity  a  central  hollow  or  depression,  around  which  is 
arranged,  in  a  circular  manner,  a  collection  of  thread-like  pro- 
jections, or  secondary  papillae.  Like  the  rest  of  the  mucous 
membrane  of  the  tongue,  they  are  covered  with  stratified  pave- 
ment-epithelium. In  the  secondary  papillae  of  the  larger  fili- 


THE  MOUTH  AND  TONGUE.  381 

form  papillae  the  epithelium  is  of  the  horny  variety,  and  its 
arrangement  is  imbricated,  the  lower  margin  of  each  scale  over- 
lapping the  upper  border  of  the  scale  next  below  it.  In  the 
axes  of  the  filiform  papillae  large-sized  arterial  and  venous 
capillaries  extend.  Each  secondary  papilla  contains  a  vascu- 
lar loop.  The  papillae  of  smallest  size  contain  a  fine  network 
of  vessels,  and  in  the  posterior  part  of  the  tongue  simple  capil- 
lary loops.  Neither  the  filiform  papillae  nor  their  secondary 
papillae  contain  nerve-fibrils.  The  latter  are  found,  however, 
at  the  base  of  the  papillae,  where  they  end  in  rounded  terminal 
bulbs. 

The  fungiform  papillce  are  larger  than  the  filiform,  and 
their  epithelial  covering  is  much  thinner.  They  appear  as 
rounded  prominences,  somewhat  constricted  at  the  base,  and 
covered  upon  the  sides  and  top  with  many  cone-shaped  second- 
ary papillae.  The  free  surface  of  some  fungiform  papillae  is 
smooth,  the  secondary  papillae  being  farther  apart.  These  are 
found  most  commonly  at  the  lateral  edges  of  the  tongue,  and 
are  the  so-called  lenticular  papillae.  The  distribution  of  the 
fungiform  papillae  is  rather  irregular,  and  it  varies  in  different 
individuals.  At  the  base  of  the  tongue,  and  generally  at  its 
lateral  portions,  between  the  filiform  papillae,  they  are  some- 
times scarce  and  sometimes  quite  abundant.  Toward  the  tip 
of  the  tongue  they  are  smaller,  while  they  are  larger  in  the 
region  of  the  circumvallate  papillae.  They  are  covered  with 
several  layers  of  pavement-epithelium,  the  deeper  strata  of 
which  are  formed  by  smaller  polygonal  prickle-cells.  In  this 
epithelial  covering,  upon  the  surface  of  the  fungiform  papillae, 
are  constantly  found  peculiar  bodies,  called  the  "  taste-goblets." 

The  taste-goblets  vary  in  size  and  shape  in  different  ani- 
mals, and  also  in  the  same  animal,  according  to  the  locality 
in  which  they  are  found.  They  usually  resemble  a  short- 
necked  flask,  their  longest  diameter  being  the  longitudinal. 
The  lower  part  of  the  taste-goblet  rests  upon  the  submucosa  ; 
the  body,  and  more  especially  the  part  which  corresponds  to 
the  neck  of  the  flask,  is  surrounded  by  epithelial  cells.  Every 
taste-goblet  has  at  the  surface  of  the  epithelium  an  opening 
called  aporus,  which  word  is  frequently  used  not  only  to  des- 
ignate the  exterior  opening,  but  also  for  the  entire  short  canal 
in  the  epithelial  layer.  The  diameter  of  the  porus  is  from 
.0064  to  .0198  mm.  It  is  surrounded  by  two  and  sometimes  by 


382  MANUAL    OF    HISTOLOGY. 

three  similarly  formed  cells.  Sometimes  the  poms  is  formed 
by  a  single  perforated  cell.  The  short  canal  in  the  epithelial 
cells  is  surrounded  in  like  manner.  In  each  taste-goblet  two 
varieties  of  cells  may  be  distinguished — the  exterior  or  super- 
ficial cells,  called  roof-  or  supporting-cells,  and  the  interior,  or 
central  cells,  called  taste-  or  rod-cells.  The  roof-cells,  which 
may  be  considered  as  modified  epithelial  cells,  surround  the 
taste-goblets  as  petals  envelop  a  bud.  Their  arrangement  with 
relation  to  one  another  is  imbricated.  The  cells  themselves 
are  long,  narrow,  spindle-shaped,  arid  curved,  and  each  one 
has  a  well-marked  nucleus.  The  peripheral  end  of  the  cell  is 
pointed,  while  the  central  extremity  is  sometimes  ramified. 
The  taste-  or  rod-cells  are  long,  slender,  and  highly  refractive. 
A  nucleus  of  unusual  size  almost  entirely  fills  their  bodies,  while 
their  extremities  pass  into  two  distinct  prolongations — the  pe- 
ripheral or  superior,  and  the  central  or  inferior.  The  peripheral 
prolongation  is  moderately  broad,  and  has  a  short,  del i< -ale 
extremity,  which  resembles  a  small  rod  or  hair.  Hence  ihe 
name  rod-cell.  These  rods  are  located  inside  the  short  canal, 
and  rarely  project  above  the  porus.  The  inferior  prolongation 
is  divided  into  several  rootlets.  The  connection  of  nerve-fila- 
ments with  the  taste-goblets  has  never  yet  been  conclusively 
demonstrated,  although  all  authorities  agree  as  to  the  proba- 
bility of  such  connection.  Many  aggregations  of  gangl ionic 
cells,  of  greater  or  less  size,  are  found  in  the  course  of  the 
nerve-bundles,  near  the  circumvallate  as  well  as  near  the  fili- 
form papilla).  In  the  fungiform  papilla)  the  nerves  enter  the 
axis  of  the  papilla)  as  small  trunks,  composed  of  fibres  with 
double  contours.  These  divide  into  single  nerve-filaments, 
some  of  which  terminate  in  bulbs,  which  are  located  in  the  lat- 
eral surfaces  of  the  fungiform  papilla),  under  the  secondary 
papilhc.  The  fibrils  which  run  into  the  axis  pass  into  pale  ter- 
minal filaments,  and  disappear  in  a  brush-like  extremity  in  a 
granular  mass  composed  of  neurilemma— its  nuclei,  and  nu- 
merous circular  granules — the  gustatory  granules.  These  last 
consist  of  a  globular  nucleus,  surrounded  by  a  very  small 
amount  of  cell-protoplasm.  The  resemblance  of  the  above  io 
the  interior  roof-cells  of  the  acoustic  terminal  apparatus,  and 
to  the  rods  and  cones  of  the  retina,  is  striking. 

The  conical  or  secondary  papillae  are  of  the  same  general 
construction  as  the  fungiform  throughout ;  but  they  present 


THE    MOUTH    AND    TONGUE.  383 

the  following  differences  of  appearance  :  their  epithelial  cover- 
ing is  thicker,  and  stratiiied  somewhat  after  the  manner  of  the 
iiliform.  papillae,  the  taste-goblets  are  absent  upon  their  sur- 
face, and  the  nerve-fibres,  so  far  as  they  can  be  traced,  termi- 
nate in  bulbs. 

The  circumvallate papilla,  about  nine  in  number,  are  situ- 
ated at  the  back  part  of  the  tongue.  They  form  an  irregular 
row  on  each  side  and  incline  slightly  from  before  backward 
toward  the  median  line.  At  their  point  of  junction  is  the  fora- 
men ccecum  of  Morgagni.  Each  circumvallate  papilla  consists 
o[  a  broad,  flat  elevation  of  the  mucous  membrane,  which  is 
surrounded  with  a  fossa.  Its  surface  is  covered  with  small 
secondary  papillae,  and  the  epithelium  is  like  that  of  the 
f uiigiform  papillae.  Taste-goblets  are  found  abundantly  upon 
the  lateral  edges  and  toward  the  centre  of  the  papillae.  The 
blood-vessels  are  arranged  as  in  the  fungiform  papillae,  and 
each  secondary  papilla  contains  a  vascular  loop.  The  nerves 
are  derived  from  the  glossopharyngeal.  They  consist  of  single 
pale  nerve-fibres,  which  form  a  network  in  the  centre  of  the 
papilla?  and  ascend  toward  its  peripheral  surface. 

The  papillae  foliate,  or  limbrhc  linguae,  consist  of  several 
folds  of  the  mucous  membrane  at  the  lateral  edges  of  the 
tongue.  Between  them  are  scattered  a  few  fungiforrn  papil- 
lae, and  they  contain  a  considerable  number  of  taste-goblets. 
Many  excretory  ducts  of  acinous  glands  empty  at  the  bases  of 
these  folds. 

The  sublingual  mucous  membrane  includes  that  of  the  floor 
of  the  mouth.  Both  are  of  the  same  structure,  and  pass  into 
each  other  by  means  of  a  reduplication,  the  fraenum  linguae. 

The  secreting  glands  of  the  root  of  the  tongue  are  of  two 
varieties—serous  and  mucous.  The  mucous  glands  are  like 
those  elswhere  in  the  buccal  cavity.  Their  ducts  are  some- 
times lined  with  ciliated  epithelium.  The  glands  themselves 
are  not  found  in  the  neighborhood  of  the  taste-goblets.  The 
serous  glands,  on  the  other  hand,  are  found  most  abundantly 
in  those  parts  of  the  tongue  which  are  most  richly  supplied 
with  taste-goblets.  Their  ducts  open  into  the  grooves  which 
are  lined  by  the  taste-goblets. 

'The  follicular  glands,  which  form  the  collections  of  adenoid 
tissue  found  at  the  base  and  at  the  sides  of  the  tongue,  are  not 
true  glands,  but  rather  elevations  of  the  mucous  membrane 


384  MANUAL    OF    HISTOLOGY. 

caused  by  circumscribed  collections  of  adenoid  tissue  found  in 
the  tunica  propria.  They  resemble  glands,  in  that  they  gener- 
ally possess  a  cavity  of  variable  size  which  terminates  at  the 
surface  of  the  follicle.  The  mass  of  adenoid  tissue  which  com- 
poses the  follicle  is  surrounded  by  fibres  of  connective  tissue, 
which  are  sometimes  so  compactly  woven  as  to  form  almost  a 
capsule  around  it.  Sometimes  this  capsule  is  wanting,  but  a 
gradual  transition  of  the  two  neighboring  forms  of  tissue  is 
never  seen.  Above,  the  adenoid  tissue  extends  as  far  as  the 
epithelium,  so  that  the  papillae  of  the  mucous  membrane  either 
disappear  altogether  or  are  only  to  be  found  occasionally,  and 
then  of  small  size.  This  adenoid  tissue  is  in  all  its  essentials 
similar  to  that  found  in  the  tonsils,  the  vault  of  the  pharynx, 
and  at  scattered  points  in  the  adjacent  tissues. 

The  so-called  mucous  corpuscles  of  the  saliva  are  probably 
lymph  corpuscles  which  have  escaped  from  the  adenoid  tissue 
just  mentioned. 


BIBLIOGRAPHY. 

ALBINUS.  Academicarnm  AnDotationum.  Lib.  I.  S.  58.  (Quoted  by  J.  Honig- 
schmied.)  Leidoe,  1754. 

BOPP.     Die  Verrichtungen  des  fiinften  Nervenpaares.     Leipsig,  1832. 

ELSASSER,  in  F.  Majendie  Lehrbuch  der  Physiologic,  aus  dem  Franzosischen  uber- 
setzt  mit  Anmerkungen  und  Zusatzen  von  D.  C.  L.  Elsasser.  3  Aufl.  I.  Tu- 
bingen, 1834. 

MAYER,  J.  F.  C.  Neue  Untersuchungen  aus  dem  Gebiete  der  Anatomie  und  Phy- 
siologie.  S.  25  und  26.  Bonn,  1842. 

BRUHL.  Ueber  das  Mayer'  sche  Organ  an  der  Zunge  der  Haus-Saugethiere  oder  die 
seitliche  Zungenriicken-Druse  derselben.  Vierteljahrschrift  fur  wiss.  Veter- 
inarkunde.  I.  S.  165.  Wien,  1851.  Kleine  Beitrage  zur  Anatomie  der  Haus- 
Saugethiere.  Wien,  1850. 

KOLLIKER,  A.  Microscopische  Anatomie.  II.  Specielle  Gewebelehre.  2.  Halfte. 
1.  Abth.  Leipzig,  1852. 

SCHWALBE.  Das  Epithel  der  Papillae  vallatae.  Vorlaufige  Mittheilung.  Arch.  f. 
microscop.  Anat.  III.  S.  504.  1867.  Derselbe  Ueber  die  Geschmacks- 
organe  d.  Saugethiere  und  des  Menschen.  Arch,  f .  microscop.  Anat.  IV.  S. 
154.  1867.  Und  M.  Schultze,  Erklarung  der  Entdeckung  der  Schmeck- 
becher  von  G.  Schwalbe  betreffend.  Arch,  f .  mikroskop.  Anat.  VIII.  S.  660. 
1872. 

LOVEN.  Beitrage  zur  Kentniss  vom  Bau  der  Geschmackswarzchen  der  Zunge.  Arch, 
f.  mikroskop.  Anat.  IV.  8.96.  1867. 

SCHWALBE.  Zur  Kentniss  der  Papillae  fungiformes  d.  Saugethiere.  Centralblatt 
f.  d,  med.  Wiss.  Nr.  28.  S.  433.  1868. 


BIBLIOGRAPHY.  385 

VON  WYSS.     Ueber  ein   neues  Geschmacksorgan   auf   der  Zunge  des  Kaiiinchens. 

Centralblatt  f.  d.  med.  Wiss.      Nr.  35.     S.  548.     1869.     Derselbe,  Die  becher- 

formigen  Organe  der  Zunge.     M.  Schultze.     Arch,  fur  mikroskop.  Anat.     VI. 

S.  238. 
KKAUSE.    Die  Nervenendigung  in  der  Zunge  des  Menschen.     Gottinger  Nachrichten. 

S.  423.     1870. 
VERSON.     Beitrage  zur  Kentniss  des  Kehlkopfes  und  der  Trachea.     Sitzgsbr.  der 

wiener  Acad.     1  Abth.     LVII.      S.  1093.      1868.      Derselbe,  Kehlkopf  und 

Trachea  in  Strickers  Handbuch  der  Lehre  von  den  Geweben.     I.     S.  456. 

Leipzig,  1871. 
HONIGSCHMIED,  J.     Beitrage   zur  mikroskop.    Auatomie    der    Geschmacksorgane. 

Ztschr.  f.  wissensch.  Zool.     XXIII.     S.  414. 

EXNER.     Med.  chirurg.  Rundschau,  Juni  Heft.     S.  400.     Wien,  1872. 
DITLEVSEN.     Undersogelse  over  Smaglogene  paatungun  hos  patte  dyrene  og  men- 

nesket.     Kopenhagen,  1872.     Referat  in  Hoffmann  und  Schwalbe  Jahresb.    I. 

Lib.     S.  211.     1872. 
HONIGSCHMIED.     Ein  Beitrag  iib.  die  Verbreitung  der  becherformigen  Organe  auf 

der  Zunge  der   Siiugethiere.     Centralbl.  f.  d.  med.  Wiss.     No.  26.     S.  401. 

1872. 
HENLE.     Handbuch  der  system.  Anatomic  des  Menschen.     II.     2.  Aufl.     S.  873. 

1873. 
VON  EBNER,  RITTER.     Die  acinosen  Driisen  der  Zunge  und  ihre  Beziehungen  zu  den 

Geschmacksorganen.     Gratz,  1873. 
SERTOLI,  E.     Osservazioni  sulle  terminazioni  dei  nervi  del  gusto.     Gazetta  Medico- 

Veterinaria.     IV.    2.     Separatabdruck.     Deutsch   in   Molesch.  Unters.      XL 

4.  Heft.     S.  403.     1874. 
HOFFMANN,  A.     Ueber  die  Verbreitung  der   Geschmacksorgane    beim   Menschen. 

Arch.  f.  pathol.  Anat.     LXII.     S.  516.     1875. 
WATSON,  W.  SPENCER.     Diseases  of  the  Nose  and  its  Accessory  Cavities.     London, 

1875. 
VON  BRUNN.     Untersuchungen   iiber  das  Riechepithelium.      Arch,    f .   mik.  Anat. 

No.  11.     1875. 

KRAUSE,  W.     Allgemeine  und  mikroskop.  Anat.     Hannover,  1876. 
VOLTOLINI.     Address  delivered  December  15,  1876,  before  the  Silesian  Association 

for  National  Culture. 
KRAUSE.     Lehrbuch.     Hannover,  1876. 
KOLLIKER.   Ueber  die  Jacobson'schen  Organe  des  Menschen.   Festschrift  zu  Rineckers 

Jubilaum.     Leipzig,  1877. 

PONCHET  et  TOURNEUX.     Precis  d'histologie  humaine.     1878. 
LUSCHKA.     Das  Epithelium  der  Riechschleimhaut  des  Menschen.     Centralbl.  f.  die 

med  Wissenschaft.     Nr.  22.     1877. 

WUNDT.     Lehrbuch  der  Physiologic  des  Menschen.     Stuttgart,  1878. 
25 


CHAPTER  XXIV. 

THE  ALIMENTARY  CANAL. 

BY  EDMUND  C.  WENDT,  M.D., 

Curator  of  the  St.  Francis'  Hospital,  etc.,  New  York  City. 

THE  human  alimentary  canal  is  a  tube  of  great  length,  ex- 
tending from  the  mouth  to  the  anus.  There  are  considerable 
variations  of  its  calibre  in  the  different  regions  of  the  body 
through  which  it  passes.  The  two  external  openings  of  the 
digestive  tract  are  continuous  with  the  cutaneous  surface  of 
the  body.  Throughout  its  entire  extent  we  find  several  super- 
imposed layers  or  membranes,  which  are  from  within  outward  : 
1,  a  mucous  membrane  with  its  submucosa  ;  2,  the  muscular 
coat ;  and  3,  a  fibrous  layer.  In  addition  to  these  fundamental 
strata,  we  encounter  certain  special  structures,  which  charac- 
terize the  various  parts  of  the  canal.  The  buccal  cavity  and 
pharynx  are  elsewhere  described ;  we  begin,  therefore,  with  a 
consideration  of 

THE   (ESOPHAGUS. 

The  wall's  of  this  section  of  the  tract  are  directly  continuous 
with  those  of  the  pharynx,  and  have  an  average  thickness  of 
from  three  to  four  millimetres.  In  the  oesophagus,  in  addition 
to  the  four  pharyngeal  coats,  a  new  layer  appears  between  the 
epithelial  stratum  and  the  submucous  tissue.  This  new  struc- 
ture has  received  the  name  of  muscularis  mucosse.  Hence,  the 
different  layers  of  the  oesophagus  are  from  within  outward  : 

1.  The  mucous  membrane. 

2.  The  muscularis  mucosse 

3.  A  submucous  layer. 

4.  The  muscular  coat. 

5.  A  fibrous  envelope. 

The  mucous  membrane  presents  comparatively  long,  coni- 


THE    (ESOPHAGUS. 


387 


cal  papillae  of  more  or  less  dense  connective  tissue,  containing 
looped  blood-vessels,  and  lined  throughout  by  stratified  pave- 
ment-epithelium. These  papillae  attain  a  marked  degree  of 
development  in  the  adult  only.  In  infancy  their  future  pres- 
ence is  indicated  by  a  wavy 
outline  at  the  internal  attached 
border  of  the  epithelial  stratum. 
This  latter  portion  of  the  mu- 
cous membrane  con  tributes  0.22 
— 0.26  mm.  toward  the  entire 
oesophageal  thickness  of  about 
4.0  millimetres. 

The  muscularis  mucoscB  con- 
sists chiefly  of  longitudinal,  un- 
striped  muscle-cells.  They  are 
disposed  in  bundles  of  differ- 
ent sizes,  separated  by  varying 
amounts  of  connective  tissue. 
Toward  the  inferior  portion  of 
the  oesophagus  these  bundles 
approach  each  other,  displacing 
the  interposed  tissue,  and  form- 
ing finally  one  continuous  mus- 
cular layer.  The  thickness  of  this  layer  varies  between  0.2 
and  0.3  mm. 

The  submucous  layer  is  made  up  of  fasciculated  connective 
tissue  and  elastic  fibres.  It  contains  groups  of  fat-cells,  and 
lodges  the  mucous  glands.  The  latter  closely  resemble  the 
glands  found  in  the  mouth.  They  consist  of  pyramidal  or  poly- 
gonal secret  ing-cells  with  conspicuous  rounded  nuclei,  and  ducts 
lined  by  cylindrical  epithelia.  The  lower  portion  of  the  cesoph- 
agus  contains  smaller  and  more  superficial  acinous  glands. 
In  this  region  they  are  also  found  in  greater  abundance,  and 
around  the  cardiac  orifice  they  form  almost  a  complete  ring. 

The  muscular  coat  has  an  inner  circular  and  an  outer  longi- 
tudinal layer.  In  man  it  is  formed  of  both  varieties  of  muscle- 
cells,  the  striped  and  unstriped.  The  upper  portion  is  composed 
of  striped  muscle  only,  whereas  the  lower  half  consists  exclu- 
sively of  the  unstriped  variety.  Below  the  upper  one-eighth  of 
the  oesophagus  smooth  muscle-cells  first  begin  to  be  blended 
with  the  other  variety ;  they  rapidly  increase  as  we  proceed 


FIG.  164. — Transverse  section  through  the 
lower  part  of  the  oesophagus  of  the  newly-born 
child  :  a,  a,  epithelium ;  &,  mucosa ;  c,  muscu- 
laris  mucosae ;  d,  Bubmucotis  tissue ;  «,  layer  of 
circular  muscular  fibres  ;  /,  longitudinal  muscu- 
lar layer ;  a,  external  fibrous  layer  ;  A,  A,  two  of 
the  ganglia  of  Auerbach.  Klein. 


388  MANUAL    OF    HISTOLOGY. 

downward,  until  at  about  the  middle  of  its  course  the  striped 
fibres  entirely  disappear,  being  replaced  by  continuous  layers 
of  unstriped  muscle-cells. 

The  fibrous  envelope  consists  of  connective  tissue  and  elastic 
fibres,  arranged  so  as  to  form  a  thin,  peripheral,  sheath-like 
membrane. 

Blood-vessels  and  lymphatics  are  found  in  less  abundance 
in  the  oesophagus  than  in  the  mouth  and  pharynx.  The  for- 
mer are  arranged  in  the  shape  of  capillary  networks  in  the 
mucosa.  The  papillary  loops,  already  mentioned,  take  their 
origin  from  these  reticula.  The  larger  branches  are  found  in 
the  submucosa.  The  lymphatics  occur  as  plexuses;  one  is 
situated  superficially  in  the  mucous  membrane,  and  communi- 
cates by  capillary  vessels,  with  a  second  larger  one,  placed  in  the 
submucosa.  The  glands  are  said  to  have  special  lymphatics. 

Nerves. — An  elaborate  account  of  the  mode  of  distribution  of 
nerves  in  the  oesophagus  is  given  in  Ranvier's  "  Legons  d'ana- 
tomie  generale,"  1880,  p.  366  et  seq.  The  following  brief  sum- 
mary gives  the  main  points :  Nervous  filaments  proceeding  from 
the  pneumogastrics  find  their  way  to  the  striped  muscles,  where 
they  terminate  in  the  well-known  eminences  ordinarily  found  in 
that  tissue.  These  terminal  bodies  are  seeir  to  be  very  numer- 
ous, a  fact  which  corresponds  to  the  importance  and  complex- 
ity of  nervous  action  concerned  in  the  process  of  deglutition. 
The  terminal  distribution  in  the  unstriped  muscle  presents  no 
striking  peculiarity.  Between  the  two  layers  of  the  muscle- 
coat  we  find -an  arrangement  analogous  to  Auerbach's  gangli- 
onic  plexus,  but  the  ganglia  and  their  nerve-cells  are  larger  and 
appear  to  be  more  numerous  than  in  the  intestine.  The  nerve- 
fibres  proceeding  from  the  vagus  are  medullated ;  those  from 
the  ganglionic  plexus  belong  of  course  to  the  non-medullated 
variety. 

THE    STOMACH. 

The  serous  covering  of  this  organ  has  the  same  general 
structure  as  all  visceral  peritoneum,  being  composed  of  a  con- 
nective-tissue membrane  lined  by  flat  endothelial  cells. 

The  muscular  coat  of  the  stomach  is  divisible  into  three 
layers,  composed  of,  1,  external  longitudinal  fibres ;  2,  middle 
circular ;  and  3,  internal  oblique  fibres.  All  of  these  belong 


THE    STOMACH. 


389 


exclusively  to  the  unstriped  variety  of  muscle-cells.  A 
thickening  of  the  inner  circular  layer  constitutes  the  pyloric 
sphincter. 

The  submucous  layer  is  composed  of  loose  connective  tis- 
sue, and  it  is  for  this  reason  that  the  mucous  membrane  is  so 
freely  movable  over  the  muscular  coat.  It  is,  moreover,  owing 
to  this  peculiarity  that, 
whenever  and  wherever 
muscular  contraction  takes 
place,  the  mucous  mem- 
brane presents  numerous 
folds,  ridges,  and  eleva- 
tions. Thus,  we  may  find 
in  a  perfectly  healthy  stom- 
ach appearances  quite  an- 
alogous' to  those  described 
by  pathologists  as  the  so- 
called  etat  mamelonne  of 
gastritis. 

The  muscularis  mucosce 
frequently  presents  two  lay- 
ers of  un  striped  muscle- 
cells — an  outer  longitudinal 
and  an  inner  circular  one. 
In  some  regions  we  observe 
only  one  layer  of  longitu- 
dinal muscle-cells. 

The  gastric  mucous  mem- 
brane is  covered  by  a  single 
layer  of  columnar  epitheli- 
um, containing  goblet-cells 
in  greater  or  less  abun- 
dance. These  goblet-cells 
represent  ordinary  epithelia,  which  appear  to  be  bulged  out 
by  mucoid  contents.  At  the  cardiac  extremity  of  the  stomach 
there  is  a  sharp,  serrated  line  of  demarcation  between  the 
O3sophageal  and  gastric  epithelial  lining.  The  surface-epithe- 
lium forms  one  continuous  stratum,  and  is  continued  down 
into  the  ducts  of  the  gastric  glands.  The  latter  occur  in  two 
distinct  varieties,  viz.,  peptic  glands  and  pyloric  glands. 

The  peptic  glands,  also  called  gastric  glands,  are  cylindrical 


FIG.  165. — Transverse  section  through  the  fundus  of 
the  stomach  in  a  child  :  o,  a,  cylindrical  epithelium ; 
6,  6,  peptic  tubes  ;  c,  c,  muscularis  mucosae  ;  d,  d,  pub- 
imicous  tissue ;  «,  circular  muscular  layer ;  /,  longi- 
tudinal muscular  layer  ;  fir,  peritoneum  ;  A,  #,  ganglion 
of  Auerbach.  Klein. 


390 


MANUAL    OF   HISTOLOGY. 


tubules,  nearly  straight  or  slightly  tortuous,  with  often  a  single 
rounded  csecal  extremity.  However,  the  latter  is  sometimes 
double  by  dichotomous  division,  or  we  find  many  such  blind 
terminal  branches.  Hence,  we  may  speak  of  simple  peptic 
glands  and  compound  peptic  glands.  They  are  all  placed  ver- 
tically to  the  surface, 
and  consist  of  a  homo- 
geneous basement-mem- 
brane with  a  lining  of 
secreting  epithelia.  (Fig. 
166.)  The  basement- 
membrane  contains  flat- 
tened nuclei,  and  at  its 
inner  aspect  it  is  fur- 
nished with  flat,  branch- 
ing adventitial  cells. 
Each  gland  is  divisible 
into  a  duct  and  gland 
proper.  The  latter, 
again,  consists  of  a  neck, 
body,  and  fundus. 

Usually,  two,  three, 
or  even  more  of  these 
glands,  have  a  common 
duct.  The  length  of  the 
entire  structure  varies  in 
the  different  gastric  re- 
gions from  0.4 — 2.0  mm., 
in  accordance  with  the 
thickness  of  the  entire 
mucous  membrane  in  the 
respective  parts.  The 
duct,  amounting  to 
about  one-fourth  of  the 

chief  cells.     B,  compound   Rastric  gland.  '  Only  the' outline^      whnlp  Ipnfrth  of  thp  til hp 
denoting  the  membrana  propria,  is  drawn.  lejeilglllOl   ILK    LUUe, 

is  lined  with  one  contin- 
uous layer  of  columnar  epithelial  cells,  similar  to  the  surface 
epithelium  of  the  rest  of  the  stomach.  The  neck,  the  thin- 
nest portion  of  the  minute  tube,  has  similar  cells ;  but  they 
appear  shorter,  darker,  and  have  a  smaller  ovoid  nucleus.  As 
regards  its  breadth,  the  body  stands  about  midway  between 


Fio.  166.— A,  simple  gastric  gland:   P,  parietal;  and  0, 


THE    STOMACH.  391 

the  neck  and  the  f  undus,  which  latter  is  the  thickest  portion 
of  the  entire  gland.  In  the  neck  we  also  find,  in  addition  to 
the  cells  already  described,  other  corpuscles  placed  externally 
to  the  former.  They  are  the  parietal  cells  (Heidenhain),  or 
delomorphous  cells  (Rollett),  the  former  variety  being  termed 
chief  cells  (Heidenhain),  or  adelomorphous  cells  (Rollett),  or 
simply  peptic  cells.  The  parietal  cells  occur  as  spheroidal, 
oval,  or  polygonal,  rather  opaque,  sometimes  very  granular 
bodies,  which  lie  beneath  the  basement-membrane,  but  com- 
monly outside  the  layer  of  ordinary  chief  cells.  In  the  body 
of  the  gland- tube  we  again  meet  with  these  two  forms  of  lin- 
ing-corpuscles. Here,  however,  the  columnar  or  chief  cells  are 
longer  than  in  the  neck,  and  their  bodies  generally  appear 
more  transparent,  while  the  nuclei,  again  spheroidal,  are  situ- 
ated nearer  the  external  than  the  internal  border.  Klein  de- 
scribes the  substance  of  these  cells  as  consisting  of  a  delicate 
reticulum,  with  a  small  amount  of  a  hyaline  interstitial  sub- 
stance in  its  meshes.  The  same  author,  also,  invariably  finds 
an  intra-nuclear  network.  Others  have  been  less  fortunate  in 
finding  such  appearances.  The  parietal  cells  of  the  body  in 
all  respects  resemble  those  of  the  neck.  As  the  fundus  is  ap- 
proached their  number  grows  comparatively  less. 

The  pyloric  glands,  which  some  histologists  insist  on  call- 
ing mucous  glands,  are  lined  throughout  by  a  single  layer  of 
epithelium.  This  is  composed  of  the  ordinary  columnar  cells 
of  the  gastric  surface.  But  the  corpuscles  here  appear  to  be 
somewhat  compressed,  so  that  they  seem  less  transparent  than 
elsewhere.  They  are  known  to  undergo  certain  changes  dur- 
ing their  passage  from  activity  to  rest.  Examined  in  the 
latter  condition,  we  find  them  more  granular,  and  apparently 
smaller  or  shorter,  than  during  and  immediately  after  secre- 
tion. These  glands  have  long  ducts,  each  one  serving  for  sev- 
eral secreting  tubules.  Their  bodies  are  branched,  and  usually 
appear  somewhat  tortuous.  When  such  glandules  become 
somewhat  more  complex  and  grow  larger  (a  change  which  nor- 
mally takes  place  in  the  duodenum),  they  are  called  Brunner'  s 
glands. 

Dr.  Edinger  has  recently  (ArcMv  f.  mikr.  Anat.,  Yol. 
XVII.,  p.  193)  asserted  that  the  gastric  glands  contain  in 
reality  only  one  kind  of  cellular  element.  He  based  his 
opinion  on  results  obtained  by  treating  the  almost  living  mu- 


392  MANUAL    OF    HISTOLOGY. 

cous  membrane  with  osmic  acid,  after  Nussbaum's  method. 
By  him  the  chief  cells  are  said  to  develop  into  parietal  cells, 
through  an  increas3  of  their  volume  and  a  filling  up  with  the 
gastric  ferment.  The  considerations  which  led  him  to  form 
this  opinion  are  as  follows  :  1,  the  occurrence  of  bodies  which 
represent  transition-forms  between  chief  cells  and  parietal 
cells ;  2,  the  analogy  of  this  assumed  metamorphosis  of  gas- 
tric corpuscles  (i.e.,  the  conversion  of  chief  cells  into  parietal 
cells),  with  similar  changes,  known  to  occur  in  other  glands 
during  active  secretion  ;  3,  the  fact  that  many  animals  which 
secrete  pepsin  have  only  the  parietal  cells  ;  4,  the  results  of  an 
examination  of  the  mucous  membrane  of  starving  animals, 
which  revealed  only  the  chief -cell  form  of  gastric  corpuscles  ; 
and  5,  the  apparent  discrepancy  in  the  descriptions  of  these 
bodies  by  competent  histologists — some  observers  regarding 
the  chief  cells,  others  the  parietal  cells,  as  exclusively  pepsin- 
ogenous. 

Still  more  recently,  Stohr  has  (Verhandl.  d.  p7iys.-med. 
Gesel.  in  Wurzburg,  1881,  p.  101)  studied  the  histology  of  the 
gastric  epithelium.  His  specimens  were  derived  from  the  fresh 
stomach  of  a  criminal  immediately  after  execution  of  the  latter. 
The  man  had  taken  no  nourishment  for  some  hours  before  his 
death.  The  principal  conclusions  of  Stohr  are :  1,  the  epithe- 
lia  of  the  mucous  glandules  are  not  destroyed  during  the  pro- 
cess of  secretion,  but,  like  those  of  the  true  gastric  glands,  con- 
tinue their  existence  ;  2,  the  parietal  groups  of  cells  represent 
those  portions  of  the  mucous  corpuscles  which  have  not  un- 
dergone mucoid  metamorphosis,  being  made  up  of  unaltered 
protoplasm. 

From  the  above  contradictory  statements  it  appears  that 
even  to-day  our  intimate  knowledge  of  the  gastric  mucous 
membrane,  and  especially  its  epithelia,  is  far  from  being  in  a 
satisfactory  condition.  It  will  have  to  be  reserved  for  future 
investigations  to  dispel  the  uncertainty  still  existing  with  re- 
gard to  some  of  the  most  interesting  details  of  the  physiologico- 
histological  characteristics  of  the  inner  coat  of  the  stomach. 

The  blood-vessels  of  the  stomach  have  an  arrangement  simi- 
lar to  that  of  the  oesophagus.  In  the  mucous  membrane,  how- 
ever, we  find  abundant  plexuses  of  capillary  vessels  surround- 
ing the  gastric  glands.  These  networks  intercommunicate,  and 
just  beneath  the  surface-epithelium  they  become  especially 


THE    STOMACH. 


393 


close.  From  this  point  the  veins  take  their  origin.  The  ve- 
nous rootlets  unite  in  a  stellate  manner  to  form  larger  branches, 
which  descend  almost  vertically  and  empty  into  a  venous  retic- 
ulum  situated  between  the  glandular  layer  and  the  muscularis 
mucosse,  and  just  above  a  similar  arterial  network. 

Lymphatics  abound   in  the   stomach.      They  appear    to 
arise  from  superficial  loops,  which,  anastomosing  between  the 


PIG.  167. — Lymphatics  of  the  gastric  mucous  membrane  of  the  human  adult.     Frey. 

glandular  tubules,  reach  the  fundal  zone  of  these  structures. 
There  they  form  a  network,  and  this  is  in  communication 
with  a  plexus  of  larger  vessels,  situated  in  the  submucous 
tissue. 

The  distribution  of  the  gastric  nerves  does  not  differ  mate- 
rially from  that  of  the  small  intestine,  in  the  description  of 
which  this  matter  will  receive  more  particular  attention.  Gan- 
glion-cells are  frequently  found  both  in  the  muscular  layer 
and  the  submucosa  ;  in  the  latter  we  have  a  tolerably  distinct 
plexus  of  nerve-filaments  and  ganglion-cells. 

Of  the  normal  occurrence  in  the  walls  of  the  stomach,  of 
true  lymphoid  follicles,  the  author  has  been  unable  to  find 
convincing  evidence.  Nevertheless  some  writers  assert  that 
they  are  always  to  be  found  there. 


MANUAL    OF    HISTOLOGY. 


THE   SMALL   INTESTINE. 


The  serous  coat  presents  no  structural  characteristics  pecu- 
liar to  itself,  closely  resembling  the  gastric  peritoneum.  It 
encloses  a  muscular  coat  and  the  mucous  membrane,  which  are 
held  together  by  connective  tissue.  The  average  thickness 
of  these  layers  does  not,  in  man,  exceed  1.0  mm.,  of  which 
three-fourths  belong  to  the  muscular,  and  one-fourth  to  the 


Fio.  168.—  Longitudinal  section  of  the  small  intestine  of  a  rabbit :  Z,  Z,  yilli ;  J,  crypts;  Pp,  a  Peyer's 
patch ;  K,  cap  of  a  follicle ;  S,  subnmoosa ;  m.  m,  muscularis  mucosae ;  R,  circular  muscular  layer ;  L, 
longitudinal  muscular  layer ;  P,  peritoneum.  Veraon. 

mucous  coat.  Of  course,  the  contracted  or  relaxed  condition 
of  the  intestinal  tube  at  the  time  of  measurement  will  appre- 
ciably influence  these  figures.  But  they  represent  the  general 
ordinary  average. 

The  muscular  coat  has  an  external  longitudinal  and  an  in- 
ternal circular  layer.     Between  the  two  we  find  Auerbach's 


THE    SMALL    INTESTINE. 


395 


plexus  myentericus  of  flat  nerve-fibres,  which  will  be  described 
farther  on.  The  muscle-coat  becomes  gradually  thinner  as  we 
pass  from  the  duodenum  to  the  ileo-csecal  valve.  In  the  for- 
mation of  this  thickened  fold  the  longitudinal  layer  does  not 
participate. 

The  unstriped  muscle-cells  have  an  average  length  of  0.255 
mm.,  and  are  about  0.005  mm.  broad.  They  are  arranged  in 
bundles,  surrounded  by  connective-tissue  bands,  with  which 
elastic  elements  are  abundantly  interwoven. 

The  mucous  membrane  is  thrown  into  folds,  and  is  studded 
with  closely  placed  projections,  called  villi.  The  general  di- 
rection of  these  folds,  the  valvulce  connivences  Kerkringii,  is 
parallel  to  the  transverse  course  of  the  circular  muscle-layer. 
They  run  parallel  to  one  another,  or  join  at  acute  angles. 
•  The  mill  jut  out  into  the  lumen  of  the  intestinal  canal,  as 
variously  shaped  projections,  of  an  average  length  of  0.04 — 0.6 
mm.,  and  an  average  breadth  of 
0.06—0.12  mm.  In  general  their 
form  may  be  said  to  be  conical  or 
cylindrical ;  but  we  always  en- 
counter a  great  variety  of  shapes, 
in  accordance  with  the  varying 
states  of  contraction  in  the  inus- 
cularis  mucosse.  Each  villus  con- 
sists of  a  large-meshed  reticulum 
of  connective  tissue,  infiltrated,  as 
it  were,  with  leucocytes,  and  con- 
taining flattened  corpuscles,  which 
resemble  endothelial  cells.  One  or 
several  spaces,  situated  in  the  cen- 
tre of  every  villus,  constitute  the 
origin  of  the  lacteal  tubes.  Ac- 
cording to  Briicke,  these  chyle- 
vessels  are  covered  by  thin,  but 
not  continuous  bundles  of  smooth  muscle-fibres.  Their  walls 
show  only  a  single  layer  of  ordinary  endothelial  cells,  with 
clear  oval  nuclei.  The  free  surface  of  the  villi,  like  that  of  the 
stomach,  is  covered  by  a  single  layer  of  columnar  epithelium. 
Each  cell  presents,  in  the  recent  state,  a  finely  striated  hyaline 
band  at  its  unattached  border.  This  structure  has,  at  different 
times,  received  various  interpretations,  and  even  now  opinions 


FIG.  160.— Section  of  a  villas  from  the 
intestine  of  a  rabbit :  a,  epithelium ;  ft, 
gtroma ;  c,  central  cavity.  Verson. 


396  MANUAL    OF    HISTOLOGY. 

are  much  divided  as  to  its  true  significance.  Some  histologists 
regard  the  striae  as  indicating  so  many  minute  pores  i'or  pur- 
poses of  absorptive  transmission  ;  others  believe  that  the  jux- 
taposition of  numerous  delicate  rods  explains  the  peculiar  ap- 
pearance ;  and  Klein  has  lately  asserted  them  to  be  merely 
prolongations  of  the  fibrils  of  the  cell-substance  composing 
the  epithelia.  These  striae  are  always  seen  to  run  parallel  to 
the  long  axis  of  the  cells. 

Kraus"e  also  described  as  of  normal  occurrence,  a  basal  pro- 
cess extending  at  an  obtuse  angle  from  the  attached  surface  of 
these  bodies,  and  inserted  into  the  delicately  serrated  border 
of  the  villi.  Near  its  attached  border  each  epithelium  presents 
a  bright  ovoid  nucleus,  with  one  or  more  distinct  nucleoli. 
Besides  the  ordinary  corpuscles,  we  find  interposed  between 
them  the  so-called  goblet- cells.  These  are  derived  from  the 
former  by  mucoid  infiltration  of  the  cell-body,  which  is  there- 
fore conspicuously  bulged  out.  Lymph-corpuscles  also  occur 
between  the  epithelia. 

Immediately  beneath  this  layer  we  find  a  delicate,  homo- 
geneous' basement-membrane,  composed  of  flattened  cells,  re- 
sembling endothelia. 

The  muscularis  mucosce,  or  muscle  of  Briicke,  is  made  up  of 
a  single  or  double  layer  of  smooth  muscle-cells.  When  double, 
an  inner  circular  may  be  distinguished  from  an  external  longi- 
tudinal coat,  both  being  always  very  attenuated. 

The  submucous  layer  is  formed  of  connective  tissue,  the 
supporting  framework  of  which  contains  lymphatics,  blood- 
vessels, nerves,  and  often  groups  of  fat-cells. 

The  glands  of  the  small  intestine  are  those  of  Brunner  and 
the  crypts  of  Lieberkuhn.  In  addition  to  these,  however,  there 
occur  numerous  lymphoid  follicles,  which,  when  found  singly, 
are  known  as  the  solitary  follicles,  and,  when  grouped  together, 
as  agminated  glands,  or  Peyer^ s  patches.  The  solitary  or 
closed  follicles  are  real  lymphoid  glands,  and,  like  these,  con- 
sist of  reticulated  connective  tissue,  the  meshes  of  which  are 
replete  with  lymph-corpuscles.  The  jejunum,  ileum,  and  colon 
all  contain  such  follicles,  but  the  agminated  glands  occur  in 
the  ileum,  abounding  especially  at  its  lower  part.  Around 
each  follicle  we  find  a  ring  of  villi  and  glands,  which  arrange- 
ment goes  by  the  name  of  corona  tubulorum  (Miiller).  The 
follicles  receive  an  enveloping  layer  of  fibro-connective  tissue. 


THE    SMALL    INTESTINE. 


397 


Brunner^s  glands  lie  in  the  submucosa,  where  they  form 
closely  crowded  tubules,  separated  by  a  small  amount  of  con- 
nective tissue.  Smooth  muscle-cells,  starting  from  the  muscu- 
laris  mucosse,  are  of  ten  seen  to  pass  between  them.  These  con- 
voluted tubules  resemble  and  correspond  to  the  gastric  glands, 
but  have  here  attained  a  much  greater  degree  of  development. 


k 


FIG.  170.— Vertical  section  throuerh  a  human  Peyer's  patch,  with  its  lymphatics  injected :  a.  intestinal 
villi  with  their  lactea's  ;  6,  Lieberkuhnian  glands;  c,  muscular  layer  of  the  mucous  membrane;  rf,  apex 
of  the  follicle  ;  e,  middle  zone  of  the  follicle ;  /,  basis  portion  of  the  follicle  ;  g,  continuation  of  the  lacteals 
of  the  intestinal  villi  into  the  mucous  membrane  proper :  A,  reticular  expansion  of  the  lymphatics  in  the 
middle  zone  ;  i,  their  course  at  the  base  of  the  follicle  ;  *,  continuation  into  the  lymphatics  of  the  submu- 
cous  tissue  ;  I,  follicular  tissue  in  the  latter.  Frey. 

They  also  appear  to  have  been  pushed  down,  as  it  were,  from 
the  mucous  into  the  submucous  layer. 

An  individual  gland  consists  of  its  long  duct  lined  by  col- 
umnar epithelium,  and  the  branched  tubules,  which  frequently 
have  terminal  clusters,  resembling  true  acini.  They  are,  how- 
ever, only  secondary  or  tertiary  diverticula,  so  that  Brunner's 
glands  really  conform  to  the  compound  tubular  type  of  secret- 
ing structures  (Renaut).  Each  ultimate  diverticulum  has  an 
external  membrana  propria  composed  of  flattened  endothelial 
cells,  and  a  lining  of  cylindrical,  columnar,  or  prismatic  secret- 
ing epithelia,  containing  oval  nuclei. 

Histologists  have  described  minute  capillary  channels  pro- 
ceeding from  the  central  lumen  of  the  gland,  between  the  se-  j 
creting-cells,   ending  just  underneath  the  membrana  propria. 
The  author  believes  these  intercellular  channels,  as  they  have 


398 


MANUAL    OF    HISTOLOGY. 


been  called,  to  be  the  artificially  altered  cement-substance  al- 
ways present  between  such  adjacent  cells.  Brunner's  glands 
abound  only  in  the  duodenum,  but  a  few  may  occasionally  be 
seen  lower  down  the  intestine.  Their  ducts,  after  traversing 
the  muscularis  mucosse,  ascend  almost  vertically  between  the 
crypts,  opening  on  the  free  surface  of  the  mucous  membrane. 


Fig.  171. — Crypts  and  interfollicular  connective  tissue,  from  the  intestine  of  the  rabbit :  K,  crypt ; 
o,  a,  epithelium ;  d,  adenoid  tissue,  from  which  the  cells  have  been  removed  by  pencilling ;  T,  fibrous 
tissue  on  the  opposite  side.  Verson. 


These  crypts  represent  open  spaces  within  the  so-called 
follicles  of  LieberkuTin,  which  are  tubular  glands  placed  verti- 
cally in  the  intestinal  mucous  membrane,  existing  throughout 
its  entire  extent. 

They  form  a  continuous  layer,  except  where  the  upward 
projection  of  a  lymph-follicle  creates  an  interruption.  These 
glands  open  at  the  base  of  the  villi,  the  epithelial  covering  of 
the  latter  being  continued  down  into  the  tubular  depressions 
which  they  constitute  in  the  mucous  membrane.  The  cells  of 
this  stratum  naturally  appear  broader  at  their  attached  than  at 


THE    SMALL    INTESTINE.  399 

their  free  extremities.  A  continuation  of  the  villous  basement- 
membrane  forms  the  membrana  propria  of  the  crypts  of  Lie- 
berkuhn.  External  to  this  we  find  the  surrounding  connective 
tissue,  which  is  disposed  in  reticula,  containing  many  leuco- 
cytes in  its  meshes.  Hence  it  is  also  known  as  adenoid  tissue. 

The  blood-vessels  enter  and  leave  the  intestine  at  the  me- 
senteric  margin.  The  arteries,  generally  accompanied  by  one 
or  two  veins,  pierce  the  muscle-coat,  giving  off  branches  which 
form  networks  in  those  layers,  then  enter  the  submucosa,  where 
they  run  parallel  to  the  surface  of  the  mucous  membrane,  and 
finally  send  off  vertical  arfcerioles  at  the  base  of  the  villi.  The 
latter  ascend  on  one  side  of  the  villus,  and  then  suddenly 
divide  into  a  dense  capillary  network.  This  division  takes 
place  near  the  middle,  the  capillaries  then  spreading  out  to  the 
apex  and  periphery.  Here  they  become  quite  superficial,  being 
covered  by  the  epithelial  lining  only.  The  venous  rootlets  of 
the  villus  are  generally  two,  or  even  three  in  number.  About 
the  glands  and  follicles  we  encounter  special  networks  with 
variously  shaped  meshes. 

Lymphatics  are  found  in  all  the  layers  of  the  intestinal 
canal.  Those  of  the  serous  coat  empty  into  the  large  mesen- 
teric  trunks.  In  an  inward  direction  we  also  find  a  network  of 
lymph-capillaries  between  the  two  layers  of  the  muscle-coat. 
The  submucous  layer  contains  the  perifollicular  lymph-sinuses 
situated  at  the  base  of  these  bodies,  and  a  reticulum  of  larger 
channels,  many  of  which  are  found  provided  with  valves.  The 
lymphatics  of  the  mucous  membrane  are  present  in  the  shape 
of  capillary  networks  surrounding  the  intestinal  glands. 

In  the  villi  we  note,  as  already  stated,  one  or  more  central 
lacteals,  communicating  at  the  base  of  these  structures  with 
the  lymph-vascular  networks  situated  around  and  between  the 
glands. 

The  nerves  of  the  intestine  are  known  as  the  plexus  of 
Auerbach,  and  of  Meissner.  The  former,  situated  between 
the  circular  and  longitudinal  fibres  of  the  musculosa,  is  com- 
posed of  flattened  nerve-branches,  made  up  of  numerous  ulti- 
mate fibrils.  Small  nodules,  containing  characteristic  gan- 
glion-cells, are  also  found,  while  little  twigs  are  given  off  from 
the  plexus  myentericus,  to  be  distributed  to  the  layers  of  the 
musculosa. 

The  plexus  of  Meissner  is  situated  in  the  submucous  tis- 


400 


MANUAL    OF    HISTOLOGY. 


sue.  Its  component  nerves  are  less  flattened,  but  are  likewise 
provided  with  ganglia  containing  variously  shaped  ganglion- 
cells.  This  plexus  also  gives  origin  to  the  secondary  networks 
of  the  muscularis  mucosse,  and  is  besides  connected  by  certain 
branches  with  Auerbach'  s  plexus. 


THE   LARGE   INTESTINE. 

The  histological  structure  of  the  colon,  broadly  speaking, 
very  nearly  resembles  that  of  the  preceding  section  of  the  ali- 
mentary canal.  The  lining  epithelium  of  the  mucous  mem- 
brane presents  the  same  characteristic  appearances  as  in  the 


PIG.  172.— Section  of  the  largre  intestine  of  a  rabbit:  J",  crypts  of  Lleberkiihn  :  a,  epithelium  ;  &,  mu- 
cosa  ;  m,  muscularis  mucosae  ;  *,  submucosa  :  R,  circular  muscular  layer ;  £,  longitudinal  muscular  layer ; 
p,  peritoneum.  Verson. 

small  intestine.  The  mucosa  of  the  colon  is,  however,  devoid 
of  villi ;  but  it  shows  numerous  crescentic  folds.  The  muscu- 
laris mucosse  will  be  found  to  answer  to  the  description  already 
given  of  that  layer  in  the  small  intestine. 

The  submucosa  also  shows  the  same  morphological  compo- 
sition, but  appears  to  be  much  richer  in  deposits  of  fat-cells. 
Aggregations  of  lymph-follicles  are  not  generally  found,  but 
large,  conspicuous  solitary  glands  abound  throughout. 

The  crypts  of  Lieberkiihn  are  identical  with  the  glands  of 


THE   RECTUM.  401 

the  same  name  found  in  the  small  intestine.  As  we  approach 
the  rectum  an  increase  in  their  length  becomes  apparent. 

In  the  vermiform  appendix  we  find  the  collection  of  solitary 
lymph-follicles  so  closely  placed  that  the  space  left  between 
adjoining  glands  does  not  equal  in  diameter  that  of  these  struc- 
tures themselves. 

The  longitudinal  layer  of  the  muscle-coat  is  quite  thin  be- 
tween the  taenise  coli,  or  flat  longitudinal  bands  of  the  large 
intestine.  These  bands  themselves  represent  thickened  layers 
of  the  musculosa.  It  appears  that  the  circular  fibres  are  espe- 
cially developed  in  the  portions  between  the  sacculi  of  the 
caecum  and  colon. 

The  blood-vessels  are  arranged  after  the  same  plan  as  in  the 
small  intestine.  In  the  submucosa  are  contained  large  trunks, 
running  parallel  to  the  surface.  Capillaries  arise  from  these, 
and  ascend  almost  vertically  between  the  crypts  of  Lieberkuhn, 
the  capillary  network  surrounding  those  structures  being  only 
moderately  developed. 

As  regards  the  lymphatics,  they  have  a  distributipn  similar 
in  all  essential  respects  to  that  found  in  the  small  intestine. 

The  nerves  likewise  imitate  in  their  structure  and  arrange- 
ment those  encountered  in  the  small  intestine.  Meissner's 
plexus  appears  to  be  provided  with  comparatively  large  gan- 
glia and  relatively  small  component  cells.  The  plexus  of 
Auerbach  also  attains  conspicuous  development  in  the  large 
intestine. 

THE   KECTUM. 

The  internal  sphincter  ani  represents  a  thickening  of  the 
circular  layer  of  the  muscle-coat.  In  its  upper  portion  the 
rectal  mucous  membrane  is  like  the  same  structure  of  the  large 
intestine.  Lower  down  we  find  the  columnar  epithelium  grad- 
ually replaced  by  stratified  pavement-epithelium. 

The  follicles  of  Lieberkuhn  are  large  and  long.  Finally, 
the  mucous  membrane  gradually  passes  into  the  ordinary  in- 
tegument surrounding  the  anal  orifice. 

The  blood-vessels,  lymphatics,  and  nerves  resemble  in  their 
distribution  those  of  the  colon,  and  are  devoid  of  characteristic 
peculiarities. 
26 


402  MANUAL    OF   HISTOLOGY. 


BIBLIOGRAPHY. 

BCEHM.     De  glandularum  intest.  struct,  penit.     BeroL,  1835. 

HENLE.     Symbol,  ad  anat.  vill.  intest.     Berol.,  1837. 

BISCHOPP.     In  Miiller's  Archiv,  p.  503,  1838. 

WASMANN.     De  digestione  nonnulla.     Berol.,  1839. 

MIDDELDORPP.     De  glandulis  Brunnianis.     Vratisl.,  1846. 

BRETTAUER  and  STEINACH.     Unt.  iiber  d.  Cylinderepithel.     Vienna,  1857. 

LEYDIG.     Histologie.     1857. 

AUERBACH.     Ueber  einen  Plexus  myentericus.     Breslau,  1862. 

AUERBACH.     Virch.  Arch.,  Vol.  XXXIII. ,  p.  340.  1865. 

LETZERICH.     In  Virchow's  Archiv,  Vol.  XXXVII.,  p.  232.     1866. 

EIMER.     Zur  Geschichte  der  Becherzellen.     Berlin,  1868. 

SCHWALBE.     Arch.  f.  mikros.  Anat.,  Vol.  VIII.,  p.  92.     1872. 

HEIDENHAIN.     Arch.  f.  mikros.  Anat.,  Vol.  VIII.,  p.  279.     1872. 

GERLACH.     Ber.  d.  sachs.  Ges.  der  Wiss.     Leipzig,  February,  1873. 

KRAUSE.     Handb.  d.  menschl.  Anat.,  Band  I.     1876. 

F.  HOFFMANN.      Die  Follikel  des  Diinndarms  beim  Menschen.     Munich,  1878. 

SERTOLI.     Contribuzioni  all'  anatomia  della  mucosa  gastrica.     Arch,  di  med.  veter. 

Fasc.  3,  p.  15.  1878. 
RUDINGER.     Beitr.  z.   Morphol.  d.  Gaumenseg.  u.  des  Verdauungsapp.     Stuttgart, 

1879. 
H  SEW  ALL.     Devel.  and  Regen.  of  the  Gastric  Gland,  EpitheL,  etc.     Journal  of 

Phys.,  Vol.  I.,  p.  321.     1879. 
EDINGER.     Zur  Kenntniss  d.  Driisenzellen  d.  Magens.     Arch.  f.  mikros.  Anat.,  Vol. 

XVII.,  p.  193.     1879. 

RANVIER.     Les  muscles  de  1'cesophage.     Journ.  de  micrographie,  III.,  p.  9.      1879. 
RENATJT,  G.     Note  sur  la  structure  des  glandes  a  mucus  du  duodenum.     Gaz.  med. 

de  Paris,  No.  41,  1879,  and  Progres  med.,  No.  23,  p.  439.     1879. 
RANVIER.     Lemons  d'anat.  generate.     Paris,  1880. 
P.  STOHR.     Ueber  das  Epithel.  des  menschl,  Magens.     Verhandl.   der  phys.-med. 

Gesellschaft  in  Wiirzburg,  p.  101.     1881. 


CHAPTER  XXV. 

THE     SPLEEN,     PANCBEAS,     THYMUS,     THYROID    AND     PINEAL 
GLANDS,  AND  PITUITAEY  BODY. 

Br  C.  L.  DANA,  A.M.,  M.D., 

Professor  of  Physiology  in  the  Woman's  Medical  College,  New  York  City. 

THE   SPLEEN. 

General  structure. — This  organ  is  composed  of  connective 
tissue  and  muscular  fibres,  containing  Malpigliian  corpuscles, 
pulp-substance,  blood-vessels,  lymphatics,  and  nerves.  An 
outline  of  the  general  arrangement  of  these  several  elements 
will  make  subsequent  details  clearer. 

Within  its  peritoneal  investment  the  spleen  has,  in  the 
first  place,  an  elastic  fibrous  capsule  ;  this  envelops  the  organ 
and  passes  into  its  interior  at  the  hilum.  From  the  internal 
surface  of  the  capsule  are  given  off  fibrous  bands  and  pro- 
cesses— the  trabeculse,  which  interlace  and  form  a  fine  network. 
In  the  meshes  of  this  network  is  a  soft,  reddish  substance — the 
splenic  pulp.  The  arteries,  entering  at  the  hilum,  run  along 
the  trabeculse  and  end  in  capillaries,  which  gradually  break  up 
in  the  parenchyma.  Attached  to  the  walls  of  the  arterioles 
and  bathed  in  the  spleen-pulp  are  little  bodies,  called  the 
MalpigMan  corpuscles.  The  veins  begin  in  the  pulp,  and, 
gradually  enlarging,  pass  out  alongside  the  arteries.  The 
blood  thus  passes  out  of  the  capillaries  into  the  spleen -pulp, 
and  from  thence  is  collected  by  the  veins.  It  passes  through 
the  blood-paths  in  the  pulp  much  as  the  lymph  passes  through 
lymph-paths  in  the  lymphatic  glands. 

This  unique  structure  is  now  to  be  considered  in  detail. 

The  peritoneal  or  serous  coat  of  the  spleen  resembles  the 
peritoneum  elsewhere.  It  is,  in  man  especially,  very  firmly 


404  MANUAL    OF    HISTOLOGY. 

adherent  to  the  fibrous  coat  beneath  it,  and  closely  invests  the 
organ.  It  is  reflected  off  at  the  hilum  to  form  the  gastro- 
splenic  omentum,  and  also  at  the  upper  border,  where  it  in- 
vests the  suspensory  ligament. 

The  fibrous  coat,  or.  capsule  of  the  spleen,  is  white  in  color, 
and  thicker  than  the  serous  coat.  It  is  composed  of  fibrous 
tissue,  which  is  permeated  very  extensively  by  elastic  fibres. 
Mingled  with  them  are  a  few  smooth,  muscular  elements.  At 
the  hilum  this  fibro-muscular  coat  surrounds  the  vessels  and 
nerves  and  passes  into  the  substance  of  the  spleen  with  them, 
forming  what  is  called  the  "capsule  of  Malpighi."  It  invests 
the  arteries  and  veins  as  far  as  their  finer  branches,  and  gives 
off  fibrous  processes,  which  have  a  diameter  of  -fa  mm.  to 
2  mm.,  and  which  help  to  make  up  the  trabecular  frame- 
work of  the  spleen.  This  framework  is  formed  by  processes 
sent  off  from  the  internal  surface  of  the  spleen's  fibrous  coat, 
which  join  with  the  processes  sent  off  from  the  capsule  of 
Malpighi,  and  interlace  until  a  firm  network  is  made.  In  this 
structure  lie  embedded  the  spleen-pulp  and  the  Malpighian 
corpuscles.  The  fibrous  sheath  of  the  veins  has  a  somewhat 
peculiar  arrangement.  It  becomes  at  once  intimately  adherent 
to  the  venous  walls,  uniting  them  closely  with  the  surrounding 
parenchyma.  As  the  veins  grow  smaller  this  fibrous  coat  splits 
into  bands  containing  muscle-cells,  which  lie  longitudinally 
along  the  vessel-wall.  These  bands  do  not  entirely  surround 
the  vessel,  however,  but  allow  the  thin  endothelium  and  in- 
tima  to  be  seen  between  them.  They  finally  leave  the  veins 
to  join  the  trabecular  framework.  The  tissue  composing  this 
framework  is  made  up,  like  the  capsule,  of  elastic  and  other 
fibres,  with  a  good  many  smooth  muscle-fibres  arranged  longi- 
tudinally along  their  course. 

MalpigMan  corpuscles. — The  Malpighian  or  spleen  corpus- 
cles are  so  intimately  connected  with  the  arteries  that  it  will 
be  necessary  first  to  trace  in  part  the  course  of  the  latter.  The 
arteries  of  the  spleen  enter  at  the  hilum,  enclosed  in  a  common 
sheath  with  the  veins  and  accompanied  by  the  lymphatics. 
They  divide  and  subdivide  very  rapidly.  When  they  have 
reached  a  diameter  of  about  two-tenths  of  a  millimetre,  the 
veins  leave  them  and  take  an  independent  course.  At  this 
point  of  separation,  or  even  sooner,  the  outer  connective-tissue 
coat  of  the  artery  begins  to  be  transformed  into  the  ordinary 


THE   SPLEEN. 


405 


adenoid  tissue ;  the  fibrillse  become  more  delicate  and  interlace 
in  a  coarser  meshwork  ;  in  the  interstices  are  lymph-cells  and 
at  the  nodal  points  are  small  nuclei.  Klein  describes  large,  flat- 
tened endothelioid  cells,  "  endothelioid  plates,"  fixed  upon  the 
reticulum.  This  lymphoid  tissue  surrounds  the  artery  in  a 
loose  coat  of  variable  thickness.  At  certain  points  there  is  a 
local  hyperplasia  of  it ;  it  becomes  massed  into  little  ovoid  or 
spherical  bodies,  which  are  called  Malpighian  corpuscles. 
These  have  a  diameter  of  TV  to  TV  mm.  They  are  attached 
like  buds  to  the  artery,  or,  not  rarely,  the  artery  pierces  them 
centrally  or  eccentrically.  When  thus  pierced  the  lymphoid 
change  in  the  arterial  coats  extends  much  deeper.  The  cor- 
puscles resemble  very  closely  the  follicles  in  the  solitary  glands 
of  the  intestine,  as  well 
as  those  of  the  lymphatic 
glands  (Fig.  173).  They 
are  composed  of  the  same 
retiform  connective  tis- 
sue, in  the  meshes  of 
which  are  lymphoid  cells, 
with  occasionally  yellow 
or  brown  pigment.  This 
retiform  tissue  becomes 
denser  near  the  external 
part  of  the  corpuscle, 
but  no  distinct  envelop- 
ing membrane  exists.  In- 
deed, the  external  sur- 
face is  generally  connect- 
ed by  fibrillse  with  the 
branching  cells  of  the  spleen-pulp  surrounding  it.  Toward 
the  centre  the  retiform  tissue  is  more  open.  The  cells  within 
the  meshes  are  lymph-cells  of  various  sizes.  They  have  an 
average  diameter  of  TJ¥  mm.  The  smaller  ones  have  a  single 
nucleus,  the  larger  may  have  several.  An  arterial  twig  enters 
the  corpuscle  either  from  the  attached  artery  or  from  the  out- 
side. It  divides  at  once  into  capillaries,  which,  as  a  rule,  have 
no  regular  arrangement.  They  receive  an  adventitia  of  lymph- 
oid tissue.  Most  of  them  soon  lose  this  adventitia,  their  walls 
become  rich  in  nuclei,  branching  processes  are  given  off,  and 
the  structural  character  of  the  vessel  is  lost.  They  finally 


FIG.  173.— Prom  the  spleen  of  the  Tropidonotus  natrix : 
a,  follicle,  with  its  capillary  plexus ;  &,  septum,  with  venous 
plexus.  MfiUer. 


406  MANUAL    OF   HISTOLOGY. 

break  up  entirely,  and  their  contents  pass  out  at  the  periphery 
of  the  corpuscles  into  the  meshes  of  the  pulp.  It  is  to  be 
noted  that  the  Malpighian  corpuscles  are  the  only  parts  of  the 
spleen  where  capillaries  exist  to  any  extent.  The  arteries  going 
to  the  pulp  for  the  most  part  break  up  at  once. 

The  spleen-corpuscles  differ  from  the  lymph-follicles,  par- 
ticularly, in  having  fewer  capillaries,  no  lymph-paths,  and  in 
containing  pigment  in  their  meshes.  The  number  of  Malpig- 
hian corpuscles  in  a  spleen  of  ordinary  size,  as  estimated  by 
Sappey,  is  about  ten  thousand  ;  but  this  applies  to  lower  ani- 
mals. In  man  they  are  smaller  and  less  numerous.  Pro- 
tracted disease  is  thought  to  diminish  the  number. 

The  spleen-pulp. — This  is  a  soft,  reddish  brown  substance, 
looking,  when  squeezed  out,  like  grumous  blood.  On  expo- 
sure to  the  air  it  acquires  a  redder  hue.  Under  the  microscope 
it  is  found  to  present  a  honeycombed  appearance,  in  the  meshes 
of  which  are  numerous  lymph-corpuscles,  fragments  of  red 
blood-corpuscles,  so-called  nuclei,  and  pigment-granules.  Thus, 
we  have  really  only  a  modified  form  of  adenoid  tissue.  Klein 
considers  that  the  network  is  made  up  of  the  large,  flat  endo- 
thelioid  cells  above  referred  to.  Processes  branching  from 
these  and  uniting  with  each  other  form  the  meshes.  I  have 
been  unable  to  make  out  the  structure  as  Klein  describes  it, 
and  his  own  observations  and  plates  do  not  demonstrate  it 
satisfactorily.  The  branching  endothelioid  cells  are  connected 
with  the  breaking-up  and  the  beginning  of  the  blood-vessels, 
but  do  not  form  the  whole  pulp  reticulum. 

The  fibrillfiB  of  this  retiform  tissue  are  connected  with  the 
external  surface  of  the  Malpighian  corpuscles,  with  the  lym- 
phoid  tissue  that  ensheaths  the  small  arteries,  with  the  fibrous 
trabeculse  of  the  spleen  itself,  and  with  the  cell-nuclei  of  the 
walls  of  the  arterioles,  capillaries,  and  venous  radicles.  From 
these  points  they  branch  and  interlace,  enclosing  the  cellular 
and  other  elements  in  their  meshes.  These  branching  fibrillsD 
are,  as  in  other  lymphoid  tissue,  of  a  pale,  granular  appearance. 
The  cells  enclosed  in  the  meshes  are  not  crowded  so  closely 
together  as  are  those  in  the  Malpighian  corpuscles  (Fig.  174). 
They  are  of  different  sizes ;  the  small  ones  are  sometimes  de- 
scribed as  free  nuclei.  The  larger  ones  have  one,  two,  or  more 
nuclei  within  them.  These  larger  cells  often  contain  red  blood- 
globules  in  various  degrees  of  disintegration,  a  fact  which  gives 


THE    SPLEEN.  407 

rise  to  the  opinion  that  one  of  the  functions  of  the  spleen  is  to 
destroy  them.  The  pigment-granules  are  found  both  without 
and  within  the  cells,  and  occasionally  even  stain  the  nodal 
nuclei  of  the  sustentacular  tissue.  The  pigment  is  yellowish, 
brown,  or  black,  and  there  is  enough  of  it  to  give  a  charac- 
teristic dark  color  to  the  gross  ap- 
pearance of  the  spleen.  In  addition 
to  the  pulp-elements  mentioned,  there 
are,  according  to  Fremke  and  Kolli- 
ker,  small,  yellowish  nucleated  cells, 
which  are  possibly  young  red  blood- 
globules. 

The  pulp-substance  thus  described 
has  arterioles  and  capillaries  ending 
and  veins  beginning  in  it.  The  blood 
flows  from  the  former,  through  the 

•i       ,  ,-i  -i-\         •      i        i-i         i     i      current;    c,  its   continuation  into   the 

SpaCeS  between  the    CellS,    intO  the    lat-    venous  roots  with  incomplete  walls;  d, 

ter.    Here  is  every  opportunity,  there-  v 

fore,  for  the  blood  to  recruit  itself  with  new  white  corpuscles, 
and  to  enrich  itself  with  albuminous  and  pigmentary  matter 
from  disintegrated  red  globules.  The  analyses  of  the  blood 
in  the  splenic  vein  seem  to  show  that  it  does  do  this. 

Blood-vessels. — We  have  already  described,  to  a  certain 
extent,  the  general  arrangement  of  the  blood-vessels,  but  some 
further  particulars  remain  to  be  noticed. 

The  splenic  artery,  the  largest  branch  of  the  coeliac  axis, 
passes  to  the  spleen  in  a  course  so  tortuous  as  to  shorten  its 
length  in  a  straight  line -by  one -third.  It  enters  the  gastro- 
splenic  omentum,  divides  generally  into  six  branches,  and 
passes  into  the  spleen  at  the  hilum,  where,  in  common  with  the 
vein,  it  becomes  surrounded  by  the  capsule  of  Malpighii.  The 
branches  then  rapidly  subdivide  and  decrease  in  size,  but  with- 
out anastomosing.  When  about  two-tenths  of  a  millimetre  in 
diameter  they  leave  the  veins  and  receive  their  sheaths  of  lym- 
phoid  tissue  and  Malpighian  bodies,  as  has  been  described. 
They  then  end  for  the  most  part  in  capillaries,  which  pass  to 
the  Malpighian  bodies  and  there  break  up  in  the  way  above 
described.  But  there  are  other  capillaries  which  pass  into  the 
pulp-substance,  where  their  walls  gradually  melt  away,  so  to 
speak,  into  the  retiform  tissue  that  surrounds  them.  If  one 
follows  this  change  with  a  microscope,  he  will  see  the  capil- 


408 


MANUAL    OF    HISTOLOGY. 


lary  tube  becoming  thinner  and  more  freely  studded  with 
nuclei ;  from  some  of  these  nuclei  processes  are  sent  out  which 
connect  with  the  fibrillse  of  the  pulp.  At  this  stage  injections 
into  the  capillaries  pass  freely  out  into  the  surrounding  tis- 
sue. The  exact  point  where  the  capillary  wall  merges  into 
the  sustentacular  tissue  can  hardly  be  determined. 

The  venous  radicles  begin  in  a  somewhat  similar  way  to 
that  in  which  the  capillaries  end  (Fig.  174).  The  sustentacu- 
lar fibrillse  (endothelioid  plates  ?)  appear  to  arrange  themselves, 
first  of  all,  in  a  circular  manner,  occasionally  interlacing  at 
right  angles  (Fig.  175).  Lying  within  and  upon  the  fibrillse 

thus  arranged  are 
oval  cells  with  promi- 
nent nuclei.  These 
nuclei  are  often  con- 
nected with  the  sus- 
tentacular fibrillse 
^  outside.  These  cells 
are  not  adherent  to 
each  other  at  first, 
but,  as  the  radicle  be- 
comes more  perfect, 
they  unite  to  form  a 
complete  wall ;  the 

FIG.  175.— From  the  pulp  of  the  human  spleen,  brushed  preparation  external  layer  of  cil'- 
(combination):  «,  pulp  strand  with  the  delicate  reticnlar  framework:  ,,        ...  , 

transverse  section  of  the  cavernous  venous  canal ;  c,  longitudinal  sec-  CUlar  IlbrillSe  tnen 
tion  of  such  an  one  ;  d,  capillary  vessel  in  a  pulp  tube,  dividing  up  at 

e ;  /,  epithelium  of  the  venous  canal ;  g,  side  view  of  the  same ;  A,  its  D  6  C  O  m  6  S  m  eta  m  O  T- 
transverse  section.  Frey. 

phosed  into  a  tunica 

intima  ;  finally,  the  thick  oval  cells  are  replaced  by  flat  endo- 
thelial  cells,  and  the  complete  venule  is  formed. 

Having  shown  how  this  vascular  channel  begins,  we  turn, 
for  convenience  of  description,  to  its  other  end.  The  splenic 
vein  enters  the  hilum,  just  as  the  artery  does.  As  it  subdi- 
vides, however,  it  loses  both  tunica  adventitia  and  tunica  me- 
dia. The  internal  tunic  remains  and  becomes  firmly  united 
with  the  fibrous  trabeculse  of  the  spleen,  so  that,  on  section, 
the  venous  wall  does  not  collapse,  but  appears  like  a  part  of 
the  parenchyma.  After  several  subdivisions  the  veins  begin 
to  anastomose,  and  they  finally  form  a  closely  reticulated  ar- 
rangement of  like-sized  vessels  having  an  average  diameter 
of  T£o-  to  Tfg-  mm.  These  are  called  the  cavernous  veins.  The 


THE    SPLEEN.  409 

branches  from  them  subdivide,  pass  into  the  pulp,  and  end  in 
the  venous  radicles  we  have  described. 

It  is  proper  to  state  that  some  authors  (Gray,  Billroth, 
Kolliker)  believe  that  the  capillaries  connect  directly  with 
these  cavernous  veins,  pouring  the  blood  into  the  lacunae  which 
they  form.  Others  (Key,  Stieda)  believe  that  the  sustenacular 
tissue  of  the  pulp  is  not  composed  of  branching  fibrillse,  but 
of  collapsed  capillaries,  which  connect  the  arteries  with  the 
venous  radicles.  Such  views  cannot  now  be  sustained. 

The  lymphatics  of  the  spleen  occur  in  two  sets :  one,  the 
trabecular,  forms  a  close  plexus  in  the  external  capsule  and 
sends  deep  branches  along  the  trabeculse,  to  communicate  with 
the  deep  or  perivascular  set.  This  perivascular  set  arises  from 
the  lymphoid  sheaths  of  the  arteries,  and  at  first  has  no  dis- 
tinct channels.  True  lymphatics  are  soon  formed,  however, 
which  run  along  the  arteries,  generally  one  on  each  side.  At 
the  hilum  they  unite  with  the  trabecular  set,  and,  passing  along 
the  gastro-splenic  omentum,  enter  the  neighboring  lymphatic 
glands. 

The  nerves  are  derived  from  the  solar  plexus  (right  and  left 
semilunar  ganglia  and  right  pneumogastric).  They  enter  the 
hilum  and  follow  the  course  of  the  arteries ;  along  their  terminal 
ramifications,  according  to  Miiller,  are  oval  ganglia,  through 
which  a  single  fine  capillary  runs.  On  section  of  the  nerves  of 
the  spleen  the  organ  dilates,  and  on  electrical  stimulation  it 
contracts. 

Development. — The  spleen  is  present  in  all  vertebrates  ex- 
cept the  septocardia  and  myxenoids  (Muller). 

The  organ  is  developed  entirely  from  the  mesoblast,  and, 
according  to  Peremeschko,  is  intimately  related  in  its  origin 
with  the  pancreas,  from  which  it  is  an  offshoot.  Its  shape  can 
be  recognized  in  the  twelfth  week.  The  capsule,  trabeculse,  and 
retiform  connective  tissue,  are  first  formed  ;  then  the  cells  and 
Malpighian  bodies  appear,  the  latter  at  about  the  middle  of 
intra-uterine  life. 

Preparation  of  spleen  for  microscopical  examination. — 
The  methods  of  preparing  the  spleen  for  examination  are  in 
general  like  those  for  preparing  lymphoid  tissue  anywhere. 
The  organ  is  very  soft,  and  the  object  to  be  aimed  at  is  to 
harden  it  without  interfering  too  much  with  its  intimate  struc- 
ture. A  good  method  is  that  of  Klein.  The  spleen  should  be 


410  MANUAL    OF   HISTOLOGY. 

first  washed  out  with  ^  per  cent,  solution  of  common  salt  until 
the  fluid  from  the  vein  is  clear.  Then  inject  y1^  per  cent,  solu- 
tion of  osmic  acid  or  Muller's  fluid  for  twenty  minutes.  Then 
place  the  spleen,  in  Muller's  fluid  for  ten  days,  at  the  end  of 
this  time  small  bits  should  be  cut  off  and  hardened  in  alcohol, 
when  it  may  be  stained  and  mounted  in  the  ordinary  way. 
The  spleen  of  man  is  best  prepared  (E.  Klein)  by  placing  small 
bits  in  a  large  excess  of  £  per  cent,  chromic  acid  for  a  week. 
Then  change  it  to  a  J  per  cent,  solution,  and  in  three  days  from 
this  to  a  -J  per  cent,  solution.  Finally,  bits  are  to  be  placed  in 
alcohol  and  hardened  in  the  usual  way. 

I  have  obtained  excellent  sections,  however,  which  answered 
very  well  for  demonstrations,  by  freezing  the  spleen  of  the 
living  cat  with  the  ether-spray,  making  sections  at  once,  and 
staining  them  with  Bismarck  brown.  In  this  way  the  retiform 
tissue  even  may  be  seen. 


THE  PANCKEAS. 

The  pancreas  is  a  compound  racemose  gland.  It  is  com- 
posed of  a  central  duct,  which  sends  off  branches  that  divide 
and  subdivide  until  they  end  after  the  usual  manner  of  race- 
mose glands,  by  opening  into  collections  of  little  vesicles  or 
acini.  This  mode  of  structure  divides  the  gland  into  small 
lobules,  between  which  runs  areolar  connective  tissue.  The 
same  tissue  envelops  the  whole  organ. 

In  each  of  the  lobules  will  be  found  a  number  of  acini 
grouped  around  the  terminal  extremity  of  a  duct.  These 
acini  consist  of  a  basement-membrane ;  lining  this  and  almost 
filling  the  acinus  are  cubical  epithelial  cells.  The  basement- 
membrane  is  composed  of  flat,  stellate  cells.  Owing  to  their 
branching,  they  do  not  form  a  completely  homogeneous  mem- 
brane. The  epithelial  cells  lining  the  acini  are  nucleated  and 
compressed  closely  together.  Their  internal  portion,  next  the 
lumen,  is  granular  ;  the  external  part  is  clear.  This  granular 
part  represents  (Heidenhain)  the  mother-ferment,  zymogen, 
which  is  transformed  subsequently  into  trypsin.  It  varies  in 
extent  with  the  activity  of  the  gland.  During  such  activity 
the  cell  is  smaller  and  the  granular  part  less.  Between  the 
cells  (Langerhaus,  Saviotti)  fine  intercellular  passages  similar 


THE    PANCREAS. 


411 


to  those  in  the  liver-lobules  have  been  described  (Fig.  176). 
These  intercellular  passages  are  claimed  by  some,  however, 
to  be  branching  processes  from  the  cells  of  the  basement-mem- 
-  brane.  Others  regard  them  as  albuminous  cement  substances, 
holding  the  secreting 
corpuscles  together. 

Langerhaus  describes 
.  branching  centro-acinal 
cells  connected  on  either 
side  with  similar  inter- 
epithelial  cells.  (See  Pit- 
uitary Body.) 

The  excretory  duct 
of  the  pancreas  is  com- 
posed of  a  basement- 
membrane  lined  with 
cells  ;  at  the  lower  por- 
tion  small  mucous 
glands  open  into  it.  The 
basement-membrane  is 
thickened  with  fibrous 
tissue  at  first;  but,  as 
the  duct  divides  up  into 
smaller  branches,  this 
disappears.  The  lining 
cells  are  columnar  in 
shape  near  the  mouth  of  the  duct ;  passing  back,  however, 
they  grow  shorter  and  more  fiat.  Finally,  on  reaching  the 
acini,  they  resemble  endothelial  cells,  and,  as  such,  line  the 
axial  cavity  of  the  acinus.  Here  they  form  the  centro-acinal 
cells  referred  to  above. 

TJie  blood-vessels  of  the  pancreas  are  numerous,  and  form  a 
close  capillary  plexus  around  the  basement-membrane  of  the 
acini. 

The  lymphatics  probably  arise  from  between  the  acini. 
They  pass  out  with  the  blood-vessels. 

The  nerves  are  supplied  from  the  solar  plexus ;  through 
,this  fibres  come  from  the  vagus.  They  end,  according  to  Pflu- 
ger,  in  a  manner  similar  to  that  of  the  salivary  glands  ;  fine 
terminal  filaments  pass  through  the  basement-membrane  into 
the  lining  cells  of  the  acini.  Section  of  the  vagus  stops  the 


FIG.  176. — Glandular  canals  of  the  rabbit's  pancreas,  after 
Saviotti :  a,  Larger  excretory  duct ;  ft,  that  of  an  acinus ;  c, 
fiuest  capillary  ducts.  Frey. 


412  MANUAL   OF   HISTOLOGY. 

secretion-  of  the  pancreas  for  a  short  time  ;  stimulation  of  its 
central  end  does  the  same.  On  section  of  all  the  nerves  going 
to  the  gland,  there  is  a  paralytic  flow  of  the  pancreatic  juice. 

Development. — The  pancreas  appears  very  early  in  foetal 
life,  developing  from  a  mass  of  mesoblastic  tissue  in  the  duo- 
denal wall.  It  is  probable  that  hypoblastic  tissue  from  the 
same  region  passes  into  it  from  the  ducts. 


THE  THYMUS   GLAND. 

The  thymus  gland  is  an  organ  whose  function  is  unknown  ; 
it  may  be  classed,  however,  on  account  of  its  structure,  with 
the  lymph-glands,  its  tissue  being  of  the  adenoid  type.  It  is 
loosely  enclosed  in  a  vascular  connective- tissue  capsule,  which 
sends  septa  and  processes  into  the  interior  of  the  organ.  These 
divide  it  up  into  small  lobules  of  the  size  of  a  pin's-head  to 
that  of  a  pea.  Within  the  lobules  are  the  characteristic  ele- 
ments of  the  gland — the  follicles — which  are  also  known  as  the 
acini,  alveoli,  or  granules.  Running  spirally  through  each  of 
the  two  long  lobes  is  a  central  band  or  canal,  and,  upon  unrav- 
elling the  gland,  the  various  lobules  are  seen  to  be  arranged 
about  this. 

The  fibrous  capsule  is  made  up  chiefly  of  white  connective 
tissue,  mingled  with  which  there  are  fine  elastic  fibres  and  stel- 
late connective-tissue  cells.  At  a  few  of  the  nodal  points  of  the 
larger  reticulating  fibres  are  found  peculiar  cavities,  lined  with 
fusiform  cells  and  containing  a  few  lymph-corpuscles.  They 
are  probably  connected  with  the  lymphatics,  and  the  fibrous 
capsule  seems,  as  a  whole,  to  be  slightly  touched  with  a 
lymphoid  metamorphosis.  The  external  surface  of  the  cap- 
sule is  covered  with  a  single  layer  of  flat  epithelial  cells.  Deep 
in  the  capsule  is  a  rich  plexus  of  vessels,  and  scattered  spar- 
ingly through  it  are  medullated  nerve-fibres. 

The  follicles. — Enclosed  in  each  of  the  lobules,  and  making 
up  its  substance,  are  from  ten  to  fifteen,  or  even  fifty  (Frey), 
small,  spherical  or  polyhedral  bodies.  These  are  the  follicles 
of  the  gland.  They  are  from  <fo  to  -^  mm.  in  diameter,  and 
resemble  very  much  the  follicles  in  the  lymphatic  glands  and 
Peyer's  patches,  but  present  a  more  embryonal  aspect.  They 
are  held  closely  together  by  the  surrounding  tissue,  which 


THE    THYMUS    GLAND. 


413 


sends  septa  down  between  them  for  a  short  distance  (Fig.  177). 
On  section  each  follicle  is  found  to  be  composed  of  a  cortical 
and  medullary  portion.     The  medullary  portion  is  often  only 
a  cavity,  and,  as  a  rule,  is  found  to  connect,  by  a  passage 
through  the  cortex,  with  a  general  cavity  in  the  centre  of  the 
lobule.     This  latter  cavity  again  connects  with  the  spiral  cen- 
tral canal.     The  follicle  is  composed  of  reticular  connective 
tissue,  in  whose  meshes  are  cells  and  the  thymic  juice.     The 
reticulum  forms  an  adventitia  for  the  blood-vessels.    In  the 
cortical  portion  this  reticular  tissue  is  made  up  of  small,  nucle- 
ated cells,  with  long,  fine,  branching  processes.    In  the  medul- 
lary portion,  when  present,  the  reticular  cells  have  large  nuclei, 
and    their    processes    are 
coarse  and  short.     Within 
the  meshes  of  the  structure 
thus    described   are   cells, 
fat-globules,      capillaries, 
and    a  peculiar,  transpar- 
ent,   acid,    viscid,  albumi- 
nous   fluid  —  the    thymic 
juice.      The   cells  are :    1, 
lymph-corpuscles,     which 
exist  in  the  greatest  abund- 
ance ;    2,    large,    granular, 
nucleated  cells  of  various 
sizes — many  of  these  have 
long   processes,  and   they 
help  to  form,  partly  by  a 
process  of  vacuolation  (Watney),  the  concentric  corpuscles  ; 
3,  giant  cells  ;  4,  the  concentric  corpiiscles  of  Hassall.    These 
last  consist  of  one  or  more  cells,  around  which  are  arranged 
concentric  layers  of  flat,  epithelioid  cells.     This  concentric  en- 
velope suggests  the  epithelial  cylinders  seen  in  carcinomatous 
growths.     One  or  two  of  these  corpuscles  may  be  enclosed  in 
another  common  envelope,  thus  forming  a  compound  concen- 
tric corpuscle.     These  corpuscles  are  strongly  refractive,  and 
are  readily  stained  with  carmine.     They  lie  near  the  arteries, 
and  have  an  intimate  relation  with  them.     According  to  Afan- 
assien,  indeed,  they  are  developed  from  the  endothelium  of  the 
arterial  wall.     There  is  a  vascular  plexus  about  the  follicles, 
from  which  capillaries  pass  into  the  interior,  forming  a  fine  net- 


Fio.  177. — Portion  of  the  calf  s  thymus,  after  His :  The 
rings  of  the  arterial  branches  (a)  and  venous  branches  (b) 
with  the  capillary  net-work  (c)  and  the  cavities  of  the 
acini  (d).  Frey. 


414  MANUAL    OF    HISTOLOGY. 

work.  They  generally  pass  in  as  far  as  the  medullary  portion 
or  central  cavity,  and  form  a  ring  about  this. 

The  central  canal,  or  band  of  the  thymus,  is  lined  with  a 
vascular  membrane,  and  communicates  with  the  central  cavi- 
ties of  the  lobules  and  follicles.  Along  its  interior  the  bulg- 
ings  of  attached  vesicles,  or  groups  of  the  same,  may  be  seen. 

Many  authorities  consider  that  the  central  cavities  in  the 
follicles  and  lobules  are  produced  artificially  by  the  break- 
ing down  of  the  very  delicate  tissue.  There  is  much  proba- 
bility that  this  is  the  case.  More  investigation,  however,  is 
needed,  and  meanwhile  the  cavities  and  canals  are  described 
as  above,  since  it  is  extremely  rare  to  find  a  human  thymus  in 
which  they  do  not  appear  to  exist,  no  matter  how  careful  the 
preparation. 

The  blood-vessels. — The  thymus  is  not  a  very  vascular 
gland.  Its  arteries  are  distributed  in  the  capsule  and  along 
the  central  band.  From  these  parts  they  pass  unaccompanied, 
as  a  rule,  by  the  veins,  to  the  interlobular  tissue,  and  are  dis- 
tributed to  the  follicles,  as  has  been  described. 

The  lymphatics  accompany  the  blood-vessels  along  the 
central  band.  From  there  it  is  stated  (His)  that  they  pass  to 
the  interlobular  tissue  and  are  distributed  around  the  follicles, 
communicating  by  minute  channels  with  the  centre  of  the  fol- 
licle. This  latter  point,  however,  lacks  confirmation. 

Development. — The  thymus  gland  is  found  in  all  vertebrates 
except  amphioxus  (Huxley).  It  is  developed,  like  the  lym- 
phatic glands,  from  the  mesoblastic  layer,  and  can  be  seen 
early  in  foetal  life.  It  appears  first  as  a  closed  tube,  which  is 
probably  (Quain)  a  mass  of  embryonic  cells  enclosed  in  a  mem- 
branous capsule.  Along  this  projections  bud  out  which  are 
gradually  transformed  into  lobules.  By  the  twelfth  week  it 
has  become  well  developed. 

The  thymus  is  an  organ  of  foetal  and  infant  life  only.  It 
grows  rapidly  until  the  second  year,  when  it  begins  to  undergo 
a  fatty  degeneration  and  atrophy.  By  the  seventh  or  eighth 
year  it  is  a  small,  fatty  mass.  This  degeneration  of  the  thy- 
mus takes  place  in  all  the  animals  which  have  the  gland. 


THE    THYKOID    BODY. 


415 


THE  THYROID   BODY. 

The  thyroid  body  is  a  dark  red,  vascular  organ,  composed 
of  two  lobes.  It  seems  very  possible  that  we  may  now  legiti- 
mately call  it  a  secreting  gland,  whose  product  acts  upon  the 
red  blood-cells,  and  is  carried  away  by  the  lymphatics. 

The  entire  organ  is  enclosed  in  a  thin,  but  firm,  fibrous  cap- 
sule. This  sends  off  processes  to  the  interior,  which  interlace, 
forming  a  sponge-like  network.  This  network  is  thin,  however, 
and  does  not  make  up  much  of  the  substance  of  the  gland.  A 
few  elastic  fibres  run  in  it.  Enclosed  in  the  meshes  of  the  frame- 
work thus  formed  are  the  vesicles  of  the  gland.  These  are 
very  numerous  and  make  up  the  bulk  of  the  organ.  They  are 
minute,  spherical,  ovoid,  or  flattened  bodies,  whose  diameter 
is  from  Tfo  mm.  in  the  embryo  to  2  mm.  in  the  adult,  and  are 
grouped  into  small  lobules  of  various  sizes.  They  consist  of 
a  homogeneous  connective-tissue  basement-membrane,  lining 
which  is  a  single  layer  of  epithelial  cells,  the  whole  enclosing 
a  yellowish,  transparent,  viscid  fluid.  The 
lining-cells,  in  adults,  measure  about  Tfg- 
mm.  in  height  and  T^F  mm.  in  width.  They 
contain  nuclei,  and  sometimes  nucleoli. 
They  are  loosely  connected  to  the  base- 
ment-membrane, and,  with  extra-uterine 
life,  begin  to  break  away  into  the  interior 
of  the  vesicle.  Baber  describes  fine,  longi- 
tudinal striae  passing  from  the  base  toward 
the  apex  of  the  cell.  These  cells  have  a 
tendency  to  undergo  colloid  degeneration. 
The  cell-body  swells  up,  and  bursting,  the 
contents  spread  out  in  the  vesicle-cavity, 
there  to  undergo  or  complete  the  metamor- 
phosis (Fig.  178)  mentioned.  According 
to  Baber,  however,  the  cells  which  undergo  this  degenera- 
tion come  from  the  connective  tissue  surrounding  the  vesicles. 
They  pass  through  the  vesicle-wall  into  its  cavity,  and  there 
gradually  break  up.  This  change  goes  on  at  the  expense  of 
*the  vesicle- wall  and  the  intervesicular  tissue,  so  that  in  time 
the  gland,  without  being  much  enlarged,  may  appear,  on  sec- 
tion, almost  like  a  single  colloid  mass. 


FIG.  178.— Colloid  metamor- 
phosis :  a,  Gland  vesicle  of  the 
rabbit;  b,  commencing  colloid 
metamorphosis  of  the  calf. 
Frey. 


416  MANUAL    OF    HISTOLOGY. 

The  normal  fluid  contents  of  the  vesicle  coagulates  with 
heat  and  alcohol,  without  losing  its  transparency.  Floating  in 
it  are  granules,  cells,  and  occasional  translucent,  curiously 
shaped  bodies  called  sympexions  (Robin).  The  cells  come 
from  the  vesicle- wall  and  the  intervesicular  tissue.  Many  of 
them  have  lost  their  nuclei.  The  "  sympexions,"  if  they  uni- 
formly occur,  have  not  been  shown  to  have  any  significance. 

Baber  has  recently  announced  the  very  interesting  fact  that 
large  numbers  of  colored  and  colorless  blood-corpuscles  are  to 
be  found  in  the  vesicle-cavities  of  the  thyroid  of  man  and  lower 
vertebrates.  The  colored  cells,  which  largely  preponderate,  are 
in  a  state  of  partial  disintegration.  This  explains  the  yellowish 
color  of  the  vesicle-contents,  and  the  inference  is  drawn  that  the 
thyroid  has  the  function  of  destroying  red  blood-corpuscles. 

The  blood-vessels  of  the  thyroid  are  quite  numerous.  They 
ramify  in  the  capsule  along  the  trabeculse,  and  finally  form  a 
rich  plexus  about  the  vesicles,  but  do  not  penetrate  the  inte- 
rior. The  walls  of  the  veins  are  united  firmly  to  the  fibrous 
reticulum  of  the  gland,  so  that  when  a  section  of  them  is  made 
they  do  not  collapse. 

The  lymphatics  form  large  and  numerous  trunks,  both  on 
the  surface  and  in  the  interior  of  the  organ.  They  originate 
by  ccecal  extremities  lying  in  the  tissue  between  the  vesicles. 
These  unite  to  form  trunks  which  surround  the  lobules,  and 
give  off  branches  that  pass  to  the  capsule.  There  a  thick,  per- 
ipheral network  is  formed,  from  which  lymph-trunks  pass  to 
the  thoracic  and  right  lymphatic  ducts.  They  contain  a  viscid 
substance  like  that  in  the  vesicles  themselves,  and  it  seems 
probable  that  they  have  something  to  do  with  carrying  off  this 
fluid. 

The  nerves  are  from  the  middle  and  inferior  cervical  gan- 
glia, but  not  (Frey)  from  the  pneumogastric.  They  enter  the 
gland  along  the  trabeculse  and  pass  between  the  vesicles.  Gan- 
glion-cells, either  single  or  in  groups,  are  met  with  in  their 
course.  The  mode  of  termination  is  not  known,  more  than 
that  they  seem  to  dwindle  away  into  fine,  terminal  fibres,  that 
are  lost  in  the  connective  tissue. 


THE    PITUITARY    BODY.  417 


THE   PINEAL   GLAND. 

The  pineal  gland,  or  conarium,  is  a  small  body,  about  the 
size  of  a  pea,  resting  upon  the  nates  and  covered  by  the  back 
part  of  the  corpus  callosum.  It  consists  of  a  fibrous  capsule 
and  framework,  lying  in  which  are  vesicles,  cells,  blood-ves- 
sels, and  sabulous  matter.  There  is  generally  a  cavity  near  the 
base  of  the  gland. 

The  interior  of  the  structure  is  divided  into  a  cortical  and 
medullary  portion.  The  former  is  composed  of  little  vesicles, 
resembling  those  of  the  pituitary  body.  The  central  portion 
is  filled  with  nerve-cells  and  sabulous  matter,  the  latter  lying 
in  the  cavity  at  the  base.  The  nerve-cells  are  of  two  kinds : 
one,  large,  TV  mm-  in  diameter,  and  giving  off  long  pro- 
cesses ;  the  other,  very  small,  T^  mm.  in  diameter,  and  giving 
off  processes,  in  the  adult.  Nerve-fibres  run  among  these 
cells,  and  connect  them  to  the  medullary  substance  of  the 
cerebral  lobes  and  to  the  crura  cerebri.  They  are  considered, 
by  Meynert,  to  be  ganglion- cells  giving  origin  to  fibres  in  the 
crura  cerebri. 

The  sabulous  matter  is  composed  of  corpora  amylacea  and 
of  earthy  salts  combined  with  animal  matter.  The  earthy 
salts  are  :  phosphate  and  carbonate  of  lime,  phosphate  of  am- 
monia, and  magnesia  (Stromeyer). 

There  is  no  doubt  that  the  pineal  gland  contains  consider- 
able nervous  tissue.  It  is  not  yet  determined,  however,  whether 
it  should  be  considered  a  ganglionic  centre  or  a  structure  of 
similar  character  to  the  suprarenal  capsules. 


THE   PITUITARY   BODY. 

The  pituitary  body  (hypophysis  cerebri}  is  notable  for  the 
peculiarity  of  its  development  and  its  uniform  presence  in  all 
vertebrates.  It  is  a  small,  reddish  gray,  vascular  mass,  ovoid 
in  shape,  and  situated  in  the  sella  turcica.  It  is  composed  of 
two  lobes,  anterior  and  posterior,  the  former  being  the  larger. 
In  structure,  the  body,  in  its  anterior  lobe,  has  some  resem- 
blance to  the  suprarenal  capsules,  being  composed  of  a  con- 
nective-tissue framework,  in  which  lie  blood-vessels  and  closed 
vesicles.  These  latter  consist  of  a  homogeneous  membrane  en- 


418  MANUAL    OF   HISTOLOGY. 

closing  nucleated  and  micleolated  cells,  mostly  epithelial  in 
character.  These  cells  generally  line  the  interior  of  the  vesicle 
and  nearly  fill  its  cavity,  so  that  on  section  the  vesicle  looks 
somewhat  like  an  acinus  of  the  pancreas.  In  the  centre  there 
is  often  a  branched  nucleated  corpuscle  connected  with  a  simi- 
lar cell  on  one  or  the  other  side  (Klein).  The  cells  vary  much 
in  size.  In  the  connective  tissue  around  the  vesicles  are  lym. 
phatic  spaces  and  blood-vessels. 

The  posterior  lobe  is  smaller,  darker,  and  more  vascular 
than  the  anterior.  During  foetal,  and  perhaps  infant  life,  it 
has  a  cavity  in  its  interior  lined  with  ciliated  epithelium  and 
connected  by  the  infundibulum  with  the  third  ventricle. 

Development. — The  pituitary  body  is  formed  by  a  diverticu- 
lum  from  the  future  mouth  (buccal  epiblast),  which  projects 
up  to  be  transformed  eventually  into  the  anterior  lobe  ;  and 
another  diverticulum  from  the  wall  of  the  vesicle  of  the  third 
ventricle,  which  projects  down  to  form  the  posterior  lobe 
(Quain).  Epiblastic  arid  mesoblastic  tissue  are  thus  united  in 
the  organ.  The  posterior  lobe  retains  its  nervous  elements  in 
the  lower  animals,  but  in  man  contains  little  besides  connective 
tissue  and  blood-vessels. 


BIBLIOGRAPHY. 

THE  SPLEEN. 

MULLER,  WM.     Ueber  den  feineren  Bau  der  Milz      Leipzig  und  Heidelberg,  1865. 
PEREMESCHKO.     Beitrage  zur  Anatomic  der  Milz,  und  Ueber  die  Entwicklung  der 

Milz.     Sitzungsberichte  der  k.  k.  Akademie.     Zu  Wien,  1867. 
STRTCKER,  S.     Manual  of  Histology.     1872. 
QUAIN.     Elements  of  Anatomy.     New  York,  1877. 
BACELLI.     Venous  Circulation  of  the  Spleen.     Med.  Times  and  Gaz.,  Vol.  I.,  p.  532. 

1878. 

SAPPEY.     Traite  d'anatomie  descriptive.     3me  ed.  rev.  et  amel.     1879. 
RANVIER,  L.     Traite  technique  d'histo'ogie.     1879  et  seq. 
KLEIN,  E.     Quarterly  Jour.  Mic.  Science.     No.  LX.,  p.  363.     1875.     Also,  Atlas  of 

Histology.     Par.  XIII.     1880. 
FRET.     Histology.     1880. 

THE  PANCREAS. 

PPLUGER,  E.  F.  W.     Strieker's  Manual  of  Histology.     1872. 
EENAUT,  J.     Sur  les  organes  lympho-glandulaires  et  le  pancreas  des  vertebres. 

Compt.  rend.  Acad.  des  Sciences.     Vol.  LXXXIX.,  p.  247.     Paris,  1879. 
FOSTER,  M.     Physiology.     1880. 


BIBLIOGRAPHY.  419 

THE  THYMUS  GLAND. 
WATNEY,  H.     Note  on  the  Minute  Anatomy  of  the  Thymus.     Proc.  Roy.  Soc.,  Vol. 

XXVII.,  p.  369.     London,  1878. 
AFANASSIEN.     Structure  of  Thymus.     Archiv  fiir  mikroskopische  Anatomic,  Band 

XIV.,  Heft  134. 

THE  THYROID  BODY. 

BOECHAT,  P.  A.     Thesis  on  the  Structure  of  the  Thyroid  Gland.     1873. 

BAUER,  E.  CRESWELL.     Researches  on  the  Minute  Structure  of  the  Thyroid  Gland. 

Philosophical  Transactions  Lond.Roy  Soc.,  Vol.  CLXVL,  Pt.  2,  p.  557.    1876. 

Proc.  Royal  Soc.,  Vol.  XXVII.,  p.  56.     London,  1878. 
ZEISS,  OTTO.    Mikroskopische  Untersuchungen  iiber  den  Bau  der  Schilddriise.   Strass- 

burg,  1877. 
POINCARE,  M.     Contribution  a  1'histoire  da  corps  thyroi'de.     Jour,  de  Panatomie, 

p.  122.    1877. 
KLEIN,  E.     Atlas  of  Histology.     Par.  XIIL     1880. 

THE  PITUITARY  BODY. 
Journal  de  medecine,  de  chirurgie  et  de  pharmacologie  do  Bruxelles,  Vol.  LXIX. , 

p.  305.     1880. 
KLEIN,  E.     Atlas  of  Histology.     Par.  XIIL     1880. 


CHAPTER  XXVI. 

THE  THICK  CUTIS  VERA. 
BY  J.  COLLINS  WARREN,  M.D. 

THE  portions  of  the  skin  usually  selected  for  liistological 
purposes  are  those  in  which  the  papillae  or  hairs  are  best  shown. 
The  glands  are  also  carefully  described  ;  but  little  attention, 
however,  has  been  given  to  the  anatomy  of  the  cutis  vera  as  an 
organ  by  itself,  consequently  those  parts  have  not  been  ex- 
amined where  it  is  found  in  its  most  highly  developed  form. 

The  skin  varies  greatly  in  thickness ;  on  the  inside  of  the 
arms  and  thighs,  and  on  the  anterior  aspect  of  the  body  gen- 
erally, it  is  much  thinner  than  behind.  In  the  former  case, 
particularly  in  delicate  women,  it  is  exceedingly  soft  and  plia- 
ble, a  thin  fold  being  easily  raised  and  rolled  between  the 
thumb  and  finger.  In  the  latter  it  is  exceedingly  thick  in  the 
back  and  shoulders  of  hardy  adults,  appearing  as  a  veritable 
hide,  being  much  thicker  than  the  skin  of  many  pachyderma- 
tous animals.  Here  it  measures  5.5  mm.  and  even  more  in 
thickness  ;  when  tanned  it  resembles  sole  leather.  This  struc- 
ture is  composed  of  bundles  of  fibres  interwoven  in  various  di- 
rections. On  the  surface  of  these  bundles  lie  the  flat  connective- 
tissue  cells,  disposed  in  rows  and  occupying  the  intervals,  the 
tissue  being  somewhat  analagous  to  tendon.  The  cutis  is,  in 
fact,  a  sort  of  tendon  or  aponeurosis  ;  from  its  under  surface 
it  sends  out  fibrous  prolongations  of  considerable  size,  and  in 
some  animals  these  are  actually  attached  to  muscles.1  In  man 
we  find  them  dipping  down  into  the  subcutaneous  fat,  in  the 
back  forming  a  very  dense  and  firm  mesh-work.  Fatty  tumors 


1 M.  Renaut :  Anatomie  generate  de  la  peau ;  Annales  de  Dermatologie  efc  de 
Syphilographie  ;  Tome  neuvieme,  No.  5  ;  Satterthwaite  :  New  York  MedicalJournal, 
July,  1875. 


THE  THICK  CUTIS  VERA. 


421 


growing  in  this  part  of  the  panniculus  adiposus  are,  for  this 
reason,  extremely  difficult  to  enucleate. 

The  papillae  are  but  imperfectly  formed,  and  are  represented 
by  an  undulating  line.  At  short  intervals  are  the  follicles  of 
the  lanugo  hairs,  which  penetrate  only  the  superficial  layers  of 
the  cutis,  the  sweep  of  whose  fibres  would  be  otherwise  un- 
broken were  it  not  for  the 
existence  of  a  structure, 
hitherto  undescribed,1  which 
connects  the  bases  of  the 
hair-follicle  with  those  parts 
in  which  we  find  the  root  of 
the  longer  hairs  imbedded 
— the  panniculus  adiposus. 
This  consists  of  a  nearly 
vertical  cleft,  or  slender  col- 
umnar-shaped space,  ex- 
tending from  the  last-named 
structure  in  a  somewhat  ob- 
lique direction  through  the 
deeper  and  middle  layers  of 
the  cutis,  and  terminating 
at  the  base  of  the  follicle 
which  rests  upon  it.  This 
space  is  occupied  by  adipose 

tissue  in  its  entire  length  ;  hence,  the  term  "  fat-columns, 
" fat-canals,"2  would  seem  to  be  an  appropriate  name. 

The  length  of  this  space  (in  very  lean  individuals  the  fat  is 
absent,  and  we  then  see  a  delicate  mesh-work  of  connective  tissue, 
and  the  trunk  of  a  blood-vessel)  is  about  4  mm.  ;  its  width 
rather  exceeds  that  of  the  hair-follicle  above.  Its  long  axis  is 
placed  at  a  slight  angle  to  that  of  the  follicle,  which  in  most 
cases  is  nearly  perpendicular  to  the  surface,  and  is  nearly 
parallel  to  that  of  the  erector  pili  muscle  (b).  At  about  the 
middle  of  this  axis  are  given  off  two  horizontal  prolongations, 
usually  partially  filled  with  fat-tissue,  appearing  like  a  pair  of 

1  In  the  latest  treatises  of  the  skin,  no  such  structure  is  described.    See  Die  Haut- 
krankheiten  fur  Aerzte  und  Studirende  von  Dr.  Gustav  Behrend.  Berlin,  1879;  Patho- 
logic und  Therapie  der  Hautkrankheiten  von  Dr.  Moriz  Kaposi.     Wien,  1879. 

2  Note  on  the  Anatomy  and  Pathology  of  the  Skin,  by  J.  C.  Warren.    Boston  Medi- 
cal and  Surgical  Journal,  April  19,  1877. 


"  FIG.  179.— Section  of  skin  from  back  of  an  adult, 
showing  colurnna  adiposa  and  lanugo  hair.  Magnified 
about  eight  diameters  :  #,  epidermis :  ft,  erector  pili  mus- 
cle ;  rf,  fat  column  ;  e,  sudoriparous  gland  ;  /,  cutis  vera ;  g, 
adipose  tissue ;  fi,  hair ;  A,  cone  fibreux  ;  p,  lateral  cleft. 


or 


422 


MANUAL    OF    HISTOLOGY. 


extended  arms,  or  the  remaining  branches  of  a  leafless  trunk  (p). 
Near  this  point  is  suspended  the  coil  of  a  sweat-gland  (e\  held 
in  place  by  a  few  delicate  fibres  which  find  their  insertion  at 
the  top  of  the  canal  or  cleft.  The  duct  of  the  gland  runs  to  the 
top  of  this  space,  whence  it  may  be  traced  to  the  side  of  the 
hair-follicle,  whence  it  finds  its  way  to  the  surface.  (In  dogs 
the  sweat-duct  opens  directly  into  the  follicle,  a  short  distance 
from  its  mouth.)  The  fibres  of  the  cutis  appear,  in  vertical  sec- 
tions, to  terminate  abruptly  at  its  edges.  There  does  not  ap- 
pear to  be  any  structure  resembling  a  "  limiting  membrane." 
At  its  base  there  is  sometimes  a  slight  widening  of  the  cleft, 
and  on  the  side  toward  which  its  axis  leans,  the  fibres  of  the 
cutis  collect  to  form  a  bundle  which  penetrates  the  subcutane- 
ous fat  (Cone  fibreux  de  la 
peau — #,  Fig.  179).  The  upper 
extremity  is  rounded  off  in 
somewhat  dome-shape. 

The  erector  pili  muscle,  tak- 
ing its  origin  from  the  papillary 
layer  of  the  cutis,  is  inserted 
partly  into  the  base  of  the  fol- 
licle, which  its  fibres  embrace, 
and  partly  into  the  apex  of  the 
fat-canal ;  in  some  sections  the 
fibres  seem  to  penetrate  this 
space,  but  probably  surround 
it,  although  some  of  them  may 
be  attached  to  those  delicate 
bands  of  fibrous  tissue  which  traverse  the  column  of  fat-cells. 
The  muscle  lies  on  the  side  corresponding  with  the  inclination 
of  the  hair  externally,  and  appears  almost  continuous  in  its 
direction  with  the  fat-column  beneath  it. 

The  sebaceous  gland  lies  between  the  muscle  and  the  follicle 
at  the  apex  of  the  angle  made  by  them  ;  a  lobe  is  found  also 
on  the  opposite  side. 

The  number  of  these  columns  corresponds  to  the  number  of 
hairs,  as  they  are  not  found  elsewhere.  In  some  sections  of 
skin,  half  an  inch  in  length,  as  many  as  five  may  be  counted  ; 
they  are  seen  to  best  advantage  in  the  thickest  portions  of  the 
skin,  but  may  be  found  on  the  shoulders  and  arms,  breast,  ab- 
domen, and  lower  extremities.  At  some  points  they  appear 


FiO.  180. — Section  of  skin  from  the  shoulder  of 
an  infant,  magnified  seventeen  diameters  :  a,  epi- 
dermis ;  &,  erector  pili  muscle ;  c,  sebaceous  gland  ; 
d,  fat-column  ;  e,  sudoriparous  gland ;  g,  adipose 
tissue ;  h,  hair. 


THE  THICK  CUTIS  VERA.  423 

as  slight  indentations  in  the  section  ;  at  others  as  long  canals. 
They  are  well  shown  in  the  skin  of  an  infant  (Figure  180),  and 
in  a  fo3tus  of  nine  months.  In  the  pig,  the  lower  border  of  the 
cutis  appears  to  the  naked  eye,  when  seen  in  section,  like  the 
teeth  of  a  saw.  Under  the  microscope,  the  apex  of  each  inden- 
tation contains  the  bulb  of  a  hair.  In  thick  hides  these  inden- 
tations become  clefts  or  canals,  and  we  find  frequently  a 
sweat-gland  situated  at  about  the  middle  of  each.  The  canals 
are  oblique,  as  are  also  the  hair-follicles,  and  the  axes  of  the 
two  are  more  nearly  parallel  than  those  in  the  human  subject. 

In  thin  skins  the  canals  are  either  so  short  as  hardly  to  pass 
for  such,  or,  if  the  hair  is  not  of  sufficient  length  to  extend  to 
the  bottom  of  the  cutis,  absent.  A  thick  skin  and  the  ex- 
istence of  downy  hairs  are,  then,  the  conditions  necessary  for 
the  presence  of  this  structure  in  its  most  marked  forms.  I  have 
not  found  them  in  the  face,  although  in  some  individuals  they 
probably  exist  there,  nor  in  the  thinner  skin  already  alluded  to. 
In  the  lip  of  the  rat  the  long  hairs  are  imbedded  in  a  transpa- 
rent, mucous-like  connective  tissue,  and  their  roots  are  sur- 
rounded by  numerous  bands  of  muscle.  It  is  interesting  to 
note  the  fact,  that  under  each  root  are  to  be  found  vertical  rows 
of  fat-cells,  arranged  end  on  end  like  the  beads  of  a  rosary,  but 
there  appears  to  be  no  cleft  in  the  surrounding  tissue  to  en- 
close them.  In  order  to  obtain  a  preparation  of  skin  which 
shows  these  structures  in  their  entire  length,  the  section  must 
be  made  vertical  to  the  surface,  and  in  a  direction  which  corre- 
sponds with  the  inclination  of  the  cleft  of  the  hair  above  the 
surface.  This  coincides  with  the  fine  folds  or  " grain"  of  the 
skin.  Sections  made  in  any  other  direction  give  but  a  frag- 
ment of  the  canal,  which  appears  then  nearly  as  an  isolated 
lobule  of  adipose  tissue.  Even  with  these  precautions  it  is 
difficult  to  obtain  a  good  specimen,  unless  the  razor  is  guided 
by  the  eye  and,  as  in  embryonic  skin,  the  canals  are  not  large 
enough  to  be  seen,  it  is  greatly  a  question  of  luck  whether  a 
good  section  can  be  obtained. 

TJie  blood-vessels  are  well  shown  by  an  injection  of  Berlin 
blue  in  the  foatus  near  full  term.  In  each  canal,  as  well  as  in 
the  intervals  between  them,  the  arterioles  which  nourish  the 
cutis  ascend  from  the  subcutaneous  system  of  vessels,  which 
forms  a  fine  net-work  in  the  panniculus  adiposus.  Those  in 
the  canals,  on  reaching  the  lateral  clefts,  bifurcate,  giving  a 


424  MANUAL    OF    HISTOLOGY. 

branch  on  either  side,  which  anastomoses  sparingly  through 
subdivisions  with  the  adjacent  arterioles  in  the  middle  layer  of 
the  cutis,  and  give  origin  to  the  papillary  and  sub-papillary 
network  of  capillaries,  which  here  can  be  considered  as  one 
and  the  same.  At  the  point  of  bifurcation  of  the  main  vessel, 
branches  are  given  off  which  ascend  farther  in  the  canal  and 
form  a  delicate  net-work  surrounding  the  sudoriparous  gland 
("  Wundernetz").  The  anastomosis  of  the  vessel  about  the 
hair- follicle  is  particularly  rich  and  fine,  and  unites  intimately 
with  the  superficial  layer  of  capillaries.  The  hair-follicle,  with 
its  subjacent  fat-column,  thus  forms  the  centre  of  a  rich  system 
of  arterioles  and  capillaries,  which  extend  from  the  panniculus 
adiposus  to  the  papillae. 

The  lymphatics. — The  following  experiments  were  made  to 
determine  the  question  of  the  presence  of  lymphatics  in  these 
canals,  and  also  to  observe  to  what  extent  fluids  and  particles, 
pressed  up  from  below,  could  be  forced  to  the  surface. 

Skin  was  taken  from  the  body  of  a  lean  adult,  twenty-four  hours  after  death. 
A  small  amount  of  the  loose  areolar  tissue  was  left  adherent  to  its  lower  sur- 
face. The  skin  being  prepared  by  warming  for  a  few  minutes  in  water  of 
about  90°  P.,  Berlin  blue  was  injected,  by  means  of  a  subcutaneous  syringe, 
into  the  loose  areolar  tissue,  which  was  rapidly  distended  by  the  fluid.  The 
specimen  was  then  thrown  into  strong  alcohol.  A  similar  fragment  of  skin 
was  stretched  like  a  drum,  over  the  end  of  a  brass  cylinder,  to  which  it  was 
firmly  attached  by  an  open  brass  cap  and  screws.  The  cylinder  being  held 
vertically,  Berlin  blue  was  poured  upon  the  skin,  the  upper  surface  of  which 
looked  downward.  A  rubber  cork,  perforated  by  a  glass  tube,  was  securely 
fastened  to  the  top  of  the  cylinder,  and  the  tube  was  connected  with  an  appa- 
ratus designed  to  exert  any  atmospheric  pressure  required.  Pressure  sufficient 
to  raise  a  column  of  mercury  twenty-eight  millimetres  was  continued  for  an 
hour  and  a  half,  the  skin  being  pressed  out  with  great  force  in  dome-shape 
at  the  bottom  of  the  cylinder,  which  was  kept  during  this  time  in  blood-warm 
water.  The  specimen  was  then  placed  in  alcohol.  It  was  observed  that  the 
injection  mass  had  gone,  at  one  or  two  points,  to  the  surface,  and  on  making 
vertical  sections  of  the  skin  the  next  day,  the  cutis  was  found  to  be  penetrated 
by  the  mass  in  vertical  blue  lines,  which  united  at  various  intervals  by  hori- 
zontal branches,  occasionally  so  numerous  as  to  present  an  almost  continuous 
blue  surface.  The  subcutaneous  areolar  tissue  was  almost  uniformly  colored 
blue. 

Opinions  on  the  character  and  distribution  of  the  lymphat- 
ics of  the  skin  seem  to  differ.  For  instance,  Neumann  de- 
scribes them  as  vessels  distributed  through  the  skin  in  two 


THE  THICK  CUTIS  VERA. 


425 


horizontal  layers — a  superficial  and  a  deep  one — the  vertical 
connection  between  the  two  being  found  only  at  comparatively 
rare  intervals.1  Renaut  regards  the  skin  as  a  lymphatic  sponge, 
the  minutest  ramification  being  but  the  space  between  the  bun- 
dles of  fibres  ;  the  coarser  differing  from  these  in  having  an 
endothelial  lining  (connective-tissue  cells  ?),  there  being  in 
neither  case  a  true  wall,  which  is  found  only  in  the  lymphatic 
vessels  of  the  subcutaneous  tissue.2  Vertical  sections  taken 
from  the  specimens  of  skin  injected  by  puncture,  showed  a 
similar,  but  not  so  complete  an  injection,  as  was  effected  by 


FIG.  181. — Injected  lymph-system  magnified  about  eight  diameters  :  a,  epidermis;  /,  cutis  vera;  ff, 
adipose  tissue ;  h,  hair. 

the  present  method.     The  latter  seems  to  possess  special  ad- 
vantage, as  a  larger  lymph  surface  is  exposed  at  one  time. 

Fig.  181  shows  the  route  taken  by  the  Berlin  blue,  which,  as 
will  be  seen,  ascends  in  nearly  vertical  columns  through  the 
fat-canals  to  the  base  of  the  hair-follicles,  going  round  the 
sides  of  the  sweat-gland.  When  a  slight  amount  only  had 
passed  into  the  canal,  a  medium  power  of  the  microscope 
showed  the  blue  lying  in  and  staining  the  tissue  accom- 
panying the  ascending  blood-vessel  in  the  so-called  "perivas- 
cular  space."  The  lateral  clefts  were  filled  with  the  mass, 

1  Zur  Kenntniss  der  Lymphgefasse  der  Haut,  von  Isidor  Neumann. 

2  Renaut.     Op.  cit. 


426  MANUAL    OF    HISTOLOGY. 

which  extended  far  enough  to  communicate  with  that  com- 
ing from  an  adjacent  column.  From  this  point  there  is  a 
delicate  and  freely  anastomosing  network,  marking  out  the 
spaces  between  the  bundles  of  fibres  of  the  cutis.  The  lateral 
anastomosis,  lower  down,  is  not  so  free,  and  in  the  uppermost 
layers,  owing  probably  to  the  compression  of  the  bundles  of 
fibres,  there  is  little  blue  to  be  seen.  From  the  top  of  the  canal 
the  injection  surrounds  the  base  of  the  hair-follicle,  on  one  side 
ascending  vertically  and  giving  off  horizontal  branches,  and 
on  the  other  following  the  interval  between  the  lower  border  of 
the  erector  pili  muscles  and  the  fibres  of  the  cutis.  The  main 
route  is  through  the  canals,  there  being  no  penetration  from 
below  elsewhere.  A  similar  method  of  injection  of  these  spaces 
is  seen  in  certain  forms  of  disease.  A  subcutaneous,  round- 
celled  sarcoma  infiltrating  the  skin,  gave  a  similar  configura- 
tion. Also  that  form  of  congenital  nsevus  which  develops  in 
the  panniculus  adiposus,  and  in  a  few  days  after  birth  begins 
to  appear  on  the  surface.  Another  instance  is  that  variety 
of  purulent  infiltration  of  the  subcutaneous  tissue,  which  is 
most  frequently  seen  under  thick  skin  and  known  as  carbun- 
cle. The  wandering  cells  find  their  way  to  the  surface  through 
these  canals,  and  thus  give  the  characteristic,  punched-out 
appearance  to  the  skin. 

It  is  evident  from  these  examples  that  a  free  communication 
exists  between  the  interspaces  of  the  fibrous  bundles  of  the 
cutis,  and  the  subcutaneous  tissue,  and  that  this  is  effected  by 
no  closed  system  of  vessels. 

The  special  function  of  these  canals  is  not  so  evident.  In 
addition  to  furnishing  a,  route  for  the  blood-vessels  and  lym- 
phatics, there  would  seem  to  be  some  connection  with  the  hair 
and  its  apparatus.  The  constant  relation  which  they  bear  to 
this  structure,  and  the  erector  pili  muscle,  would  suggest  an 
arrangement  designed  to  facilitate  the  action  of  the  muscle, 
according  to  Biesiadecki.1  This  muscle,  by  its  contraction, 
raises  the  hair  from  the  position  which  it  occupies,  nearly  hori- 
zontal to  the  surface,  to  a  vertical  one.  Any  movement  of  the 
root  of  a  lanugo  hair  would  be  well  nigh  impossible,  imbedded 
in  the  dense  tissue  of  the  cutis,  were  it  not  for  a  yielding 
structure  like  that  of  the  columns,  an  elongation  of  which 

1  Strieker's  Handbuch  der  Lehre  von  den  Geweben  des  Menschen  und  der  Thiere. 


THE  THICK  CUTIS  VERA.  427 

would  aid  the  contraction  of  the  muscle.  In  specimens  where 
the  muscle  is  found  in  a  state  of  contraction,  the  hair-follicle 
is  bent  like  a  bow,  the  root  being  drawn  through  the  arc  of  a 
circle.  The  presence  of  fat  near  the  hair-bulb  is  made  possible 
by  this  structure,  a  condition  which  is  constant  with  all  hairs. 
That  the  fat  is  not  an  incidental  feature  of  their  structure, 
which  might  be  considered  merely  a  cleft  for  the  transmission 
of  vessels,  is  rendered  probable  by  the  observation  of  rows  of 
fat-cells  beneath  each  hair  in  the  lip  of  the  rat,  where  no  special 
channels  exist,  and,  also,  by  the  fact  that  such  columns  of  fat 
do  not  accompany  the  nutrient  vessels  of  the  skin,  in  those 
parts  where  the  hairs  are  not  found.  It  seems,  therefore, 
probable,  that  this  structure  has  some  bearing  upon  the  nu- 
trition of  the  hair. 

Sweat-glands  are  found  not  only  in  these  canals,  but  else- 
where in  the  thick  cutis  ;  the  coil  of  the  gland  is  then  usually 
situated  at  a  level  a  little  below  the  middle  of  the  cutis  vera, 
and  not  in  the  subcutaneous  adipose  tissue,  as  in  thin  skin. 


CHAPTEK  XXVII. 

UEINAEY  EXCEETOEY  PASSAGES ;  SUPEAEENAL  CAPSULES. 

BY  EDMUND  C.  WENDT,  M.D.,  NEW  YORK  CITY, 
Curator  of  the  St.  Francis  Hospital,  etc. 

THE  renal  pelvis,  the  calices,  ureters,  and  bladder,  all  consist 
essentially  of  three  layers,  which  are  an  inner  mucous  mem- 
brane, a  middle  muscular  coat,  and  an  external  fibrous  layer. 

In  the 

KENAL   PELVIS 

we  find  the  mucous  membrane  lined  with  stratified  epithelium, 
the  cells  of  which  are  large  and  variously  shaped.  Three  dif- 
ferent forms  are  readily  distinguished.  The  most  superficial 
layer  consists  of  fiat  or  polyhedral  cells  of  various  sizes,  each 
one  containing  a  round  or  oval  nucleus,  or,  as  frequently  hap- 
pens, two  nuclei.  Peculiar  dark  granules,  often  of  large  size, 
surround  the  nucleus,  and  are  quite  distinct  from  the  finely 
granular  protoplasm  of  these  cells.  Then  comes  a  layer  of 
conical  or  club-shaped  bodies,  each  one  again  furnished  with 
a  round  or  oval  nucleus.  Every  cell  also  possesses  a  long 
basal  process,  which  appears  to  attach  it  to  the  subjacent 
tissue.  The  bulbous  portion  of  these  corpuscles  is  turned 
outward  in  the  direction  of  the  surface.  Wedged  in  between 
the  processes  just  mentioned  we  find  the  third  variety  of 
cellular  elements.  These  are  oval  or  rounded  bodies  contain- 
ing ellipsoid  nuclei.  At  the  renal  calices  we  find  a  sharp  line 
of  demarcation  between  the  cylindrical  columnar  epithelium 
of  the  papillary  ducts  and  the  stratified  pavement  epithelium 
of  the  pelvis.  The  epithelial  layer  has  a  thickness  here  of 
0.045-0.09  mm. 

The  connective-tissue  portion  of  the  mucous  membrane  is 
devoid  of  papillae,  contains  sparse  elastic  fibres,  and  is  rich  in 


THE    URETERS.  429 

fixed  corpuscles,  the  inoblasts  of  Krause.  There  is  no  true 
basement-membrane.  Below  this  stratum  we  find  a  submu- 
cous  layer,  which  is  abundantly  furnished  with  elastic  tissue, 
and  contains  a  few  simple  acinous  glands  with  ducts  having  a 
lining  of  cylindrical  epithelium. 

The  muscular  coat  is  composed  of  bundles  of  smooth  mus- 
cle-cells forming  an  inner  layer,  with  a  peripheral  direction  of 
its  constituent  anatomical  elements,  and  an  outer  layer  concen- 
trically arranged.  The  " papillary  sphincter"  is  but  a  thick- 
ening of  this  latter  layer. 

The  external  fibrous  layer  forms  a  thin  connective-tissue 
membrane,  not  always  clearly  marked  here,  whereas  in  the  ure- 
ters and  bladder  it  is  found  to  be  well  developed. 

The  blood-vessels  of  the  pelvis  are  derived  from  the  renal 
artery  and  vein,  and  form  capillary  networks  characterized  by 
polygonal  meshes.  The  lymphatics  and  nerves  are  found  to 
have  the  same  distribution  as  in  the  ureters. 


THE   URETERS 

have  a  structure  which  closely  resembles  that  of  the  renal  pel- 
vis. The  mucous  membrane  shows  the  same  varieties  of  epithe- 
Hum  ;  its  connective-tissue  components  are  similarly  arranged ; 
and  the  external  investing  membrane  is  composed  of  the  same 
kind  of  tissue  already  described.  But  in  addition  to  the  two 
muscular  layers^  which  here  attain  a  greater  development,  we 
find  a  third  muscle  coat,  so  that  we  can  now  distinguish  an  in- 
ternal and  external  longitudinal  from  a  middle  circular  layer 
of  muscular  elements. 

Engelmann  has  described  a  close  reticulum  of  blood  capil- 
laries lying  immediately  under  the  epithelial  stratum,  but  its 
existence  is  made  doubtful  by  the  negative  statements  of  other 
authors. 

Glandular  bodies  are  not  found  in  the  ureters.  The  peri- 
pheral layer  of  fibrous  connective- tissue  possesses  conspicuous 
elastic  bundles  in  the  lower  portion  of  the  ureters. 

The  distribution  of  the  blood-vessels  is  like  that  of  the  pel- 
vis already  described.  The  lymphatics  are  well  developed  here, 
forming  several  networks  in  the  different  layers  of  the  ducts. 
Nerves  are  likewise  readily  distinguished,  some  of  the  nerve- 


430 


MANUAL    OF   HISTOLOGY. 


fibres  being  also  furnished  with  ganglion  cells.  Their  mode  of 
termination  in  the  muscular  layer  is  not  definitely  known,  but 
may  be  assumed  to  resemble  that  of  ordinary  smooth  muscu- 
lar-tissue. 

THE   BLADDER 

has  the  same  type  of  structure  as  the  ureters,  but  contains,  in 
addition,  a  serous  covering  in  its  upper  portion.  The  different 
coats  of  the  bladder  are,  however,  much  thicker  than  the  cor- 
responding layers  in  the  other  urinary  excretory  passages. 

Th^  epithelial  lining  of  the  mucous  membrane  shows  the 
three  varieties  of  its  cellular  elements  in  a  clearly  defined  man- 
ner. 

The  connective-tissue  stratum  presents  110  noteworthy  pe- 
culiarities, if  we  ex- 
cept the  comparative 
abundance  of  simple 
acinous  glands. 

The  bundles  of 
muscle -cells  in  the 
muscular-coat  inter- 
lace, forming  irregu- 
lar, long-stretched 
meshes.  This  irregu- 
lar arrangement  pre- 
vents the  distinct  rec- 
ognition of  successive 
«,  a  ceii  of  the  layers,  each  with  a 
largely  prevailing  di- 
rection. Nevertheless, 

we  find  in  the  external  portion  of  the  muscle-coat  some  pre- 
dominance of  longitudinal  bundles,  together  with  an  abundant 
supply  of  elastic  fibres.  The  anterior  wall  and  vertex  of  the 
bladder  show  this  arrangement  very  conspicuously,  in  fact  the 
muscle-fibres  have  here  received  a  separate  name,  that  of  detru- 
sorurince.  The  vesical  neck  shows  a  tolerably  distinct  thicken- 
ing of  its  circular  muscle-fibres,  which  is  known  as  the  sphincter 
vesicce.  It  should  always  be  borne  in  mind  that  the  arrange- 
ment of  the  muscular  coat  is  apt  to  vary  in  different  individuals, 
the  description  here  given  will,  however,  be  found  to  apply  to 
the  majority  of  cases. 


FIG.  182.— Epithelium  of  the  urinary  bladder, 
second  layer ;  ft,  a  cell  of  the  first  layer  ;  c,  shows  the  first,  second, 
and  third  layers  of  the  epithelium  in  connection.     Obersteiner. 


SUPRARENAL    CAPSULES. 


431 


The  blood-vessels  form  a  capillary  network  in  the  mucous 
membrane,  which  is  situated  about  midway  between  the  epi- 
thelial stratum  and  the  muscular  coat.  In  other  respects  they 
present  no  peculiarity  worthy  of  note. 

The  lymphatics  are  less  abundant  in  the  bladder  than  in 
the  ureters.  They,  also,  lack  noteworthy  peculiarities  or 
special  features  of  interest. 

Plexuses  of  nerve-fibres  are  found  in  the  subserous  connec- 
tive-tissue, and  also  in  the  muscular  coat.  Microscopic  ganglia 
and  groups  of  ganglion  cells  are  also  met  with. 


SUPRARENAL   CAPSULES. 


The  suprarenal  capsules  (glandulce  suprarenales)  are  small 
flattened  bodies,  two  in  number,  situated  somewhat  above  and 


Fio.  1&3.—  Cellular  groups  and  trabeculae  of  the  cortical  substance,  from  the  suprarenal  capsule  of  the 
Frog.     Eberth. 

in  front  of  the  upper  end  of  either  kidney.  They  are  usually 
triangular  or  semilunar  in  shape,  although  round  and  oval 
forms  are  also  met  with.  In  structure  they  resemble  the  so- 


432 


MANUAL    OF    HISTOLOGY. 


called  blood-vascular  glands,  but  their  function  is  not  known. 

They  belong  to  the  ductless  variety  of  glands. 

Each  suprarenal  body  consists 
of  a  capsule  inclosing  the  paren- 
chyma, which  shows  a  cortical  and 
medullary  substance.  The  cap- 
sule is  formed  of  ordinary  connec- 
tive tissue  containing  many  deli- 
cate elastic  fibrils.  Externally  it 
is  surrounded  by  loose  connective 
tissue,  containing  a  greater  or  less 
proportion  of  adipose  tissue,  and 
internally  it  sends  out  trabeculse, 
which  traverse  the  entire  organ, 
thus  constituting  and  completing 
its  frame-work. 

The  cortical  substance,  as  its 
name  implies,  occupies  the  exter- 
nal portion  of  the  suprarenal  body. 
It  has  an  average  thickness  in  man 
of  0.28  to  1.12  mm.,  is  of  a  yellow- 
ish color,  and  may  be  divided  into 
three  layers  or  zones.  The  lim- 
its of  demarcation  between  these 
layers  are  much  less  marked, 
however,  than  the  corresponding 
boundary  line  between  the  corti- 
cal and  medullary  portions.  In 
the  human  being  the  external  layer 
of  the  cortex  is  distinctly  separate 

from  the  middle  one,  but  the  latter  shows  no  such  sharp  limit 

against    the    innermost    layer. 

The  cortex  is  a  friable  substance, 

and  its  broken  surface  presents 

a  striated  appearance.  Owing  to 

rapid  post-mortem  changes,  the 

cortex  in  man  is  usually  found 

to  be  separated  from  the  medul- 
lary portion  by  a  dirty  brownish 

SUbstanCe,     Containing    modified 

blood  and  cortical  corpuscles. 


PIG.  184. — Perpendicular  section  through 
the  suprarenal  capsule  of  man  :  1,  cortex  ;  2, 
medulla;  a.  capsule;  6,  layer  of  outer  cell- 
groups  ;  c,  layer  of  cell-trabeculae  (zona  fasci- 
culata);  d,  layer  of  inner  cell-groups  ;  e,  med- 
ullary substance ;  /,  transverse  section  of  a 
vein.  Eberth. 


FIG.  185.— Single  cells  and  cell-groups  of  the 
Human  suprarenal  cap- 


SUPRARENAL    CAPSULES. 


433 


The  three  layers  of  the  cortex  are  an  external  one,  or  zona 
glomerulosa  ;  a  middle  one,  or  zona  fasciculata ;  and  an  in- 
ternal one,  or  zona  retlcularis. 

The  external  layer  consists  of  rounded  or  oval  groups  of 
cells,  separated  by  delicate  connective-tissue  trabeculse,  which 
spring  from  the  capsule.  Similar  cells  are  found  throughout 
the  entire  cortex.  They  have  been  called  the  parenchymatous 
bodies  or  cells,  although  a  better  name  is  cortex  corpuscles. 
In  structure  they  resemble  ordinary  cells,  consisting  of  poly- 


FIG.  186.  — Horizontal  section  through  the  outermost  cortical  portions  of  the  suprarenal  capsule  of  the 
Horse,  a,  blind  termination  of  a  cylinder ;  ft,  groove-shaped  and  cylindrical  cortical  trabeculae ;  c,  stroma. 
Eberth. 

hedral  masses  of  protoplasm  furnished  with  spherical  nuclei 
and  conspicuous  nucleoli.  Their  protoplasm  has  a  coarsely 
granular  character,  and,  as  a  rule,  contains  more  or  less  fat  in 
greater  or  smaller  droplets. 

The  middle  layer  contains  cortical  corpuscles  which  are  ar- 
ranged in  almost  parallel  rows,  and  are  so  closely  packed  that 
this  portion  acquires  a  distinctly  striated  appearance.  These 
cellular  columns  have  received  various  names.  By  Ecker  they 
were  called  gland  tubules,  Kolliker  termed  them  cortical  cylin- 

28 


434 


MAXUAL    OF    HISTOLOGY. 


ders,  Eberth  described  them  as  cylindrical  cell-trabeculse,  or 
cortical  trabeculse,  and  Krause  named  them  cellular  pillars. 
These  cellular  rows,  columns,  or  streaks,  are  by  no  means 
always  cylindrical,  for  on  cross-section  they  frequently  present 
a  semilunar,  oval,  or  bean-shaped  appearance.  Their  inner 
and  outer  terminations  have  a  rounded  shape,  and  near  the 
former  place  they  seem  to  anastomose  with  one  another.  At 


FIG.  IS?. — Vertical  section  through  the  the  cortical  portion  of  the  suprarenal  capsule  of  the  Horse,   a, 
capsule ;   &,  cell-trabeculse  ;    c,  cell-groups.     Eberth. 

the  peripheral  end  they  sometimes  appear  groove-shaped,  or 
in  horse- shoe  form. 

Connective-tissue  processes  communicating  with  the  cap- 
sule are  found  between  the  cell  columns,  but  the  latter  are  not 
completely  isolated  by  them.  These  connective-tissue  streaks 
also  send  off  transverse  or  oblique  fibres,  so  that  occasionally 
the  cells  of  the  middle  layer  seem  to  be  inclosed  in  basket-like 
meshes.  In  addition  to  fat-droplets,  granules  of  pigment  are 


SUPRARENAL    CAPSULES. 


435 


found  in  the  cells  of  the  innermost  portion  of  the  middle 
layer. 

The  external  layer  is  made  up  of  irregularly  arranged  cor- 
tical corpuscles.  Nearly  all  the  cells  of  this  layer  contain 
pigment  granules.  The  connective-tissue  here  forms  a  reti- 
culum,  with  variously  shaped  meshes,  which  contain  greater 
or  smaller  heaps  of  cells. 

The  medullary  substance  has  a  whitish-gray  appearance,  and 
is  of  a  more  delicate  consistency  than  the  cortex.  It  consists 


FIG.  188. — Vertical  section  through  the  medullary  substance  of  the  suprarenal  capsule  of  the  Cow. 
a,  blood-vessels ;   6,  trabeculae  of  medullary  cells.     Strieker. 

of  a  network  of  connective  tissue,  which  contains  in  its  meshes 
the  medullary  corpuscles.  These  are  pale  cells  with  spherical 
nuclei  and  large  nucleoli.  They  may  assume  various  shapes. 
In  man  they  are  generally  of  an  irregularly  stellate  or  polyg- 
onal form.  Their  protoplasm  is  finely  granular,  and  they  con- 
tain, as  a  rule,  much  less  fat  and  pigment  than  the  -  cortical 
corpuscles.  Kolliker  finds  that  they  resemble  the  nerve-cells 
of  the  central  nervous  system,  but  he  adds  that  they  cannot 
be  regarded  as  such  nerve-elements.  The  medullary  cells 
assume  a  3^ellow  or  brownish  color  when  treated  with  chromate 
of  potash  or  chromic  acid.  Since  the  cortex  corpuscles  are 
not  thus  colored,  this  peculiarity  may  serve  to  distinguish  one 
cellular  variety  from  the  other. 

The  connective- tissue  framework  of  the  medulla  is  called  its 


436  MANUAL    OF   HISTOLOGY. 

stroma,  and  its  meshes  in  man  have  an  oval  or  rounded  form, 
so  that,  as  a  rule,  the  cell-groups  have  a  similar  shape.  On  the 
whole,  we  find  a  smaller  proportion  of  connective  tissue  in  the 
medulla  than  in  the  cortex. 

The  blood-vessels  of  the  suprarenal  capsules  occupy  the 
stroma,  and  are  found  in  great  abundance.  The  arterial  vessels 
arise  from  the  aorta,  the  phrenic  and  renal  arteries,  and  the 
cceliac  axis.  About  twenty  small  branches  pierce  the  capsule, 
and  are  distributed  mainly  to  the  cortex.  The  medullary  sub- 
stance is  very  rich  in  venous  plexuses.  Capillary  networks 
are  found  in  both  cortical  and  medullary  portions.  The  veins 
uniting  form  one  principal  branch,  which  passes  out  at  the  hi- 
lus  of  the  organ.  The  right  suprarenal  vein  empties  its  blood 
into  the  vena  cava  inferior,  the  left  one  into  the  vena  renalis 
sinistra. 

Lymphatics  were  seen  by  most  observers  only  at  the  sur- 
face of  the  suprarenal  capsules.  Klein,  however,  has  recently 
asserted  that  there  exists  between  the  cells  "an  anastomosing 
system  of  narrower  and  broader  clefts,  channels,  and  lacunae, 
which  belong  to  the  lymphatic  system."  This  applies  to  the 
zona  fasciculata.  In  the  other  portions  of  the  organ  the  same 
writer  also  finds  lymph-spaces,  and  lymph-sinuses,  occupying 
the  regions  "between  the  septa  and  trabeculse  of  the  frame- 
work on  the  one  hand,  and  the  cell -groups  on  the  other." 

The  nerves  occur  in  comparatively  greater  abundance  in 
these  organs  than  in  any  other  glandular  structures  of  the  hu- 
man body.  Kolliker  was  able  to  count  thirty-three  branches 
in  a  single  suprarenal  capsule  of  a  man.  They  are  derived 
from  the  renal  plexus,  the  pneumogastric  and  phrenic  nerves, 
and  semilunar  ganglion.  Yery  fine  or  medium-sized,  dark-bor- 
dered fibres  are  commonly  encountered,  and  they  abound  espe- 
cially in  the  medulla.  Ganglion-cells  are  also  frequently  seen, 
and  Virchow  has  traced  them  into  the  interior  of  the  organ.  In 
the  cortical  substances  they  are  of  rare  occurrence.  The  terminal 
distribution  of  the  nerves  has  not  been  hitherto  ascertained, 
and  it  appears  to  be  still  a  matter  of  doubt  whether  they  ter- 
minate in  the  suprarenal  body  at  all. 

.Development. — In  mammals  the  suprarenal  capsule  has  an 
independent  origin  in  a  collection  of  tissue  between  the  Wolff- 
ian  bodies  behind  the  mesentery  and  in  front  of  the  abdomi- 
nal aorta.  (Kolliker.)  The  mesoderma  at  this  point  assumes 


B1BLIOGKAPIIY.  437 

a  special  structure.  Certain  of  its  cells  form  more  or  less  cyl- 
indrical masses  with  a  reticulated  appearance.  Between  these 
cellular  groups  a  network  of  blood-vessels  is  soon  found,  so 
that  the  whole  structure  is  now  not  unlike  embryonal  hepatic 
tissue.  In  rabbits,  Kolliker  saw  the  first  traces  of  these  bodies 
about  the  twelfth  or  thirteenth  day.  On  the  sixteenth  day 
they  had  already  attained  a  length  of  1.56  mm.,  and  occupied 
a  position  along  the  vertebral  column  from  the  first  to  the  fourth 
and  part  of  the  fifth  lumbar  vertebra.  On  cross  sections  of  em- 
bryos sixteen  days  old,  Kolliker  found  that  the  suprarenal  cap- 
sules were  distinctly  separate  at  their  upper  borders,  whereas 
their  lower  ends  were  joined  together  to  form  a  single  organ. 
The  same  writer  also  found  a  nervous  ganglion  at  the  coalesced 
central  portions  of  somewhat  older  embryos. 

Behind  the  suprarenal  capsules  a  second  sympathetic 
ganglion  was  discovered.  Remak  and  v.  Brunn  do  not  in  all 
respects  corroborate  the  statements  of  Kolliker.  The  latter 
was  unable  to  ascertain  any  existing  relationship  between  the 
nervous  system  and  the  suprarenal  capsules. 


BIBLIOGRAPHY. 

BERGMANN.     De  glandulis  suprarenalibus.     Diss.  inaug.     Gottingen,  1839. 
ECKER.     Der  feinere  Bau  der  Nebennieren  beim  Menschen  und  den  vier  Wirbelthier- 

klassen,  1846.     Article  "  Blutgef  assdriisen  "  in  Wagner's  Handworterbuch  der 

Physiologic,  Bd.  IV.     1849. 

H.  FRET.     Art.   u  Suprarenal  Capsules"  in  Todd's  Cyclopaedia  of  Anat.     1849. 
REMAK.     Untersuchungen  ueber  der  Entwickelung  d.  Wirbelthiere.     Berlin,  1853- 

1855. 

VIKCHOW.     Zur  Chemie  der  Nebennieren.     Virchow's  Archiv,  1857. 
LEYDIG.     Lehrbuch  der  Histologie,  1857. 

B.  WERNER.     De  capsulis  supraren.     Dorpat  Dissertatio.     1857. 
VULPIAN.     Gaz.  med.,  p.  659.     1856;  p.  84,  1857.     Gaz.  hebd.,  p.  665,  1857, 
G.  HARLEY.     The  Histology  of  the  Suprarenal  Capsules.     Lancet,  June  5th  and 

12th,  1858. 

BARKOW.     Anat.  Unters.  ueber  die  Harnblase.     1858. 
PALLADINO.     Estratto  del  bulletino  dell'  ass  d.   natur   e  med.     Anno  I.,    No.  5. 

Napoli. 

BURCKHARDT.     Virchow's  Arch.,  Vol.  XVII.,  p.  94.     1859. 
G.  JOESTEN.     Archiv  fur  phys.  Heilkunde,  S.  97.     1864. 
A.  MOERS.     Virchow's  Archiv,  Bd.  XXIX.,  S.  386. 
HENLE.     Anatomic  des  Menschen.     Bd.  2.     1866. 


438  MANUAL    OF   HISTOLOGY. 

ARNOLD,  JUL.     Ein  Beitrag  zu  der  feineren  Structur  und  dem  Chemismus  der  Ne- 

bennieren.     Virchow's  Archiv,  Bd.  35,  S.  64.     1866. 
HOLM.     Ueber  die  nervosen  Elements  in  den  Nebennieren.     Sitzungsberichte  der 

Wiener  Akademie.     Ed.  53,  1.  Abtheilung.     1866. 
GRANDRY.     Structure  de  la  capsule  surrenale.  Journal  de  1'anatomie  et  de  la  physi- 

ologie.     1867. 

KSLLIKER.     Handbuch  der  Gewebelehre.     5.  Aufl.     1867. 
EBERTH.     Strieker's  Archiv. 
KISSELEFP.     Centralblatt,  No.  22.     1868. 

BOUVIN.     Over  der  bouw  en  de  beweging  der  Ureteres.     Utrecht,  1869. 
ENGELMANN.     Zur  Phys.  d.  Ureters.     Pfluger's  Arch.,  Vol.  II.,  p.  243.     1869. 
OBERSTEINER,  in  Strieker's  Manual. 
UNRUH.     Archiv  f.  Heilkunde,  p.  289.     1872. 
v.  BRUNN.     Archiv  f.  mikr.  Anat.,  Vol.  VIII.,  p.  618.     1872. 
EQLI.     Arch.  f.  mikros.  Anat.,  Vol.  IX.,  p.  653.     1873. 
HAMBURGER.     Zur   Histol.   d.  Nierenb.  u.   d.     Harnleiter.     Arch.  f.  mikr.  Anat, 

Vol.  XVII.,  p.  14.     1879. 

See  also  the  text-books  of  Frey,  Krause,  Kolliker,  and  Henle. 
BRAUN.     Ueber  Bau  u.  Entw.  der  Nebennieren  bei  Reptilien.  Zool.     Anzeiger,  Vol. 

II.,   No.    27,  p.  238.  1879;    und  Arbeiten  aus  d.  zool. -zootom.   Institut  in 

Wurzburg,  Vol.  V.,  p.  1.     1879. 

KOLLIKER.     Entwickelungsgeschichte  des  Menschen.     Leipzig,  1879. 
KLEIN,  and  S.  NOBLE  SMITH.     Atlas  of  Histology.     1880. 


CHAPTER  XXVIII. 

THE  MAMMARY  GLAND. 
Br  W.  H.  PORTER,  M.D.,  and  EDMUND  C.  WENDT,  M.D.,  of  New  York  City. 

General  considerations. — By  virtue  of  its  intimate  associa- 
tion with,  the  function  of  reproduction,  this  organ  occupies  a 
distinctly  peculiar  position  among  the  glands  of  the  body.  In 
the  male  it  persists  through  life  in  the  same  rudimentary  form 
which  characterizes  the  mamma  of  both  sexes  at  birth.  Only 
in  the  female,  and  in  her  only  at  certain  times,  does  this  organ 
attain  its  complete  histological  maturity.  It  may  be  borne  in 
mind,  however,  that  in  a  few  anomalous  cases,  male  beings  sup- 
plied with  fully  developed  mammary  glands  have  been  ob- 
served. 

After  conception,  and  as  pregnancy  advances,  progressive 
evolution  takes  place  within  the  mamma.  This  unfolding 
process  at  length  culminates  in  exaggerated  tissue-metamor- 
phosis, which  in  other  organs  we  should  scarcely  hesitate  to 
call  pathological.  In  fact,  Virchow  and  his  followers  all  main- 
tain that  the  secretion  of  milk  is  the  direct  result  of  a  fatty 
degeneration  of  mammary  epithelium,  and  similar  in  all  essential 
respects  to  the  processes  involved  in  the  elaboration  of  the  seba- 
ceous material  from  the  cutaneous  glands  of  that  name.  Bill- 
roth,  indeed,  calls  the  mammae  cutaneous  fat-glands  (Hautfett- 
druseri),  and  he  does  this  in  consideration  of  the  mode  of  their 
development,  and  because  they  are  placed  immediately  be- 
neath the  integument.  In  spite  of  these  statements,  however, 
we  must  maintain  that  the  mammse  are  radically  different  from 
ordinary  sebaceous  glands,  and  that  the  processes  of  secretion 
in  the  two  sets  of  glands  are  quite  distinct.  The  grounds  on 
which  we  base  this  opinion  will  be  amplified  farther  on.  The 
secretory  activity  of  the  gland,  consisting  in  the  elaboration 
of  milk,  is,  as  a  rule,  called  into  play  only  during  the  period 


440  MANUAL    OF   HISTOLOGY. 

of  rapid  growth  and  development  already  alluded  to.  In  ex- 
ceptional instances,  however,  lacteal  fluid  may  be  secreted 
during  the  extra-puerperal  period. 

The  mammae  belong  to  the  class  of  compound  acinous  or  race- 
mose glands,  and,  like  the  other  organs  of  this  group,  consist  of 
a  framework  or  stroma,  and  a  proper  secreting  structure  or 
parenchyma.  As  they  appear  to  the  naked  eye,  the  bulk  of 
the  breasts  is  not  their  secreting  parenchyma,  but  ordinary 
adipose  tissue.  This  fills  out  the  intervals  between  the  lobes 

and  lobules,  and  gives  to  the  entire 
organ  its  smooth,  round  form.  The 
different  lobes  have  separate  secretory 
ducts,  which  open  upon  the  nipple. 
These  ducts  ramify  throughout  the 
substance  of  the  gland  tissue,  and 
ultimately  carry  upon  their  terminal 
branches  the  clusters  of  secreting  vesi- 
cles, called  acini  or  alveoli.  Accord- 
ing to  Zocher  and  Hen  nig,  the  true 
glandular  substance  has  not  a  rounded 

Flo.  189.— Terminal   vesicles  and         ,  1,1  •     j       ^i 

oma  from  the  giand  of  a  nursing    shape,  but  shows  a  grouping  into  three 

woman.    Langer.  ..        ,,...  />        i   •    i 

principal  divisions,  one  of  which  ex- 
tends far  up  in  the  direction  of  the  axilla.  It  is  separated 
from  the  axillary  lymphatic  glands  only  by  a  small  amount  of 
adipose  tissue.  This  would  explain  the  ease,  readiness,  and 
frequency  with  which  these  glands  become  implicated  in  ma- 
lignant disease  of  the  mamma. 

Since  the  glands  at  birth  differ  very  widely  from  the  mammae 
of  adult  women,  and  still  more  widely  from  those  of  pregnancy, 
it  will  be  convenient  to  consider  the  histology  of  the  organ  under 
different  aspects.  This  will  be  necessary,  however,  only  with 
regard  to  the  acini  and  the  epithelia  therein  implanted,  as  these 
alone  show  such  wide  morphological  divergencies  in  the  dif- 
ferent phases  of  existence. 

The  nipple  (teat,  mamilla,  papilla  mammcB)  is  the  one  struc- 
ture belonging  to  the  mamma  which  is  least  liable  to  modifica- 
tions of  tissue  due  to  age  and  sex.  It  generally  assumes  the 
shape  of  a  pigmented  conical  or  cylindrical  projection,  at  the 
apex  of  which  the  galactophorous  ducts  have  their  terminal 
openings.  It  is  composed  principally  of  a  rather  loosely  woven 
connective  tissue,  containing  abundant  corpuscles,  and  provided 


THE    MAMMARY    GLAND.  441 

with  elastic  fibrils.  This  conjunctive  tissue  forms  a  supporting 
framework  for  the  milk-ducts  traversing  the  nipple.  The  latter 
show  walls  of  rather  dense  fibrous  tissue,  with  a  large  pro- 
portion of  elastic  elements,  and  are  provided  with  a  lining 
of  one  row  of  short  cylindrical  cells.  As  the  external  orifice 
is  approached,  these  cells  begin  to  take  on  the  character 
of  the  ordinary  epidermic  corpuscles  of  the  integument. 
Partsch  has  found  in  many  animals  that  the  secreting  paren- 
chyma accompanied  these  ducts  almost  to  their  mamillary 
orifices. 

The  occurrence  of  unstriped  muscle  in  the  nipple,  accords 
with  the  fact  of  its  erectile  properties.  But  the  exact  mode  of 
distribution  of  these  elements  is  still  a  matter  of  controversj^ 
among  histologists.  From  the  researches  of  Winkler  and 
Kolessnikow,  recently  confirmed  by  Partsch,  it  would  appear 
that  they  occur  not  in  the  ducts  themselves,  but  form  an  in- 
complete ring  around  and  external  to  the  same.  In  or  around 
the  smaller  galactophorous  ducts,  muscle-cells  cannot  be  unmis- 
takably recognized,  though  some  authors  have  described  their 
occurrence  there. 

As  regards  the  structure  of  these  smaller  galactopliorous 
ducts  (ductus  lactiferi,  milk-ducts)  it  is  quite  simple.  Their 
membranous  walls  consist  of  a  delicate  and  closely  woven 
reticulum  of  connective  tissue,  with  a  large  admixture  of  fine 
elastic  fibres.  Henle,  Meckel,  and  Kolessnikow  have  described 
smooth  muscle-cells  in  these  canals,  but,  as  already  stated, 
Partsch  and  others  have  denied  their  existence.  At  any  rate, 
on  cross- sections  the  contracted  condition  of  some  of  the  larger 
ducts  results  in  a  stellate  appearance  of  their  lumina,  whereas 
the  smaller  ducts  always  appear  round  or  oval. 

The  larger  ducts  traced  into  the  gland  tissue  are  found  to 
be  provided  with  saccular  dilatations  immediately  beneath  the 
nipple.  These  milk-reservoirs  (sinus  ductuum,  lactiferorum, 
sacculi  lactiferi,  or  ampullcE)  may  be  5  to  8  mm.  broad,  and  thus 
become  distinctly  perceptible  to  the  naked  eye.  Below  these 
dilatations  the  ducts  again  grow  narrower,  and  by  numerous 
divisions  and  subdivisions  form  a  system  of  ramifying  tubes, 
which  terminate  in  the  secreting  alveoli.  The  structure  of  the 
larger  ducts  does  not  materially  differ  from  that  of  the  smaller 
ones.  Their  walls  are,  of  course,  considerably  thicker,  and 
there  is  found  in  addition  a  greater  proportion  of  elastic  tis- 


442  MANUAL    OF    HISTOLOGY. 

sue.  All  the  different  kinds  of  ducts  show  a  lining  composed 
of  a  single  layer  of  short  cylindrical  cells,  containing  ellipsoid 
nuclei.  The  character  of  the  lining  cells  is,  however,  gradually 
changed  as  the  acini  are  approached,  near  which  it  merges  into 
the  alveolar  epithelium  by  insensible  gradations. 

Surrounding  the  nipple  is  a  variously  pigmented  ring,  called 
the  areola  mamma.  Its  surface  is  slightly  corrugated,  and 
this  circumstance,  taken  in  connection  with  its  pigmentation, 
results  in  the  production  of  the  marked  contrast  it  presents  to 
the  very  white  and  soft  integument  covering  the  other  portions 
of  the  female  mamma.  The  areola  is  also  provided  with  abun- 
dant unstriped  muscle-fibres.  Some  of  the  latter  surround  the 
nipple  in  concentric  rings,  others  pursue  a  radial  course.  The 
sudoriferous  and  sebaceous  glands  of  the  areola  are  conspic- 
uously developed,  and  lanugo  hairs  are  also  found.  The  fa- 
miliar changes  which  go  on  in  the  areola  simultaneously  with 
the  development  of  pregnancy,  are  mainly  due  to  increased 
blood-supply  and  additional  pigmentation.  The  areola  is  also 
provided  with  small  granules  of  secreting  parenchyma.  Some 
of  these  grains  empty  the  products  of  their  secretory  activity 
by  special  recurrent  ducts  into  the  main  excretory  canals.  But 
there  are  others  which  have  special  openings  upon  the  free  sur- 
face of  the  areola.  Usually,  little  papillary  eminences  mark 
the  presence  of  such  orifices.  These  scattered  bits  of  mam- 
mary parenchyma  are  known  as  the  glandules  aberrantes  of 
Montgomery.  Kolliker  and  others  regard  them  as  largely 
developed  sebaceous  glands. 

The  arteries  of  the  mamma  are  chiefly  derived  from  the 
internal  mammary  artery  and  the  long  thoracic.  The  veins 
empty  into  the  thoracic  branches  and  cephalic  vein.  Both 
arterial  and  venous  vessels  proceed  subcutaneously  from  the 
periphery  to  the  nipple,  whence  branches  are  given  off  in  a 
posterior  direction.  They  are  not  guided  in  their  course  by 
the  distribution  of  the  milk-ducts,  but  are  distributed  to  the 
glandular  parenchyma  in  such  a  way  that  each  lobule  has  its 
own  separate  supply.  Finally,  under  the  areola  the  veins  of 
the  nipple  form  a  circular  anastomosing  chain,  known  as  the 
circulus  venosus  of  Holler.  Capillary  vessels  surround  the 
acini,  forming  networks  with  rather  close  meshes.  Of  course, 
the  varying  states  of  expansion  and  contraction  in  the  ultimate 
alveoli,  which  conditions  correspond  to  phases  of  activity  and 


THE   MAMMARY    GLAND.  443 

rest,  will  materially  affect  the  size  and  shape  of  the  capillary 
networks.  They  are,  however,  much  less  distinct  and  con- 
spicuous during  the  period  of  lactation  than  in  the  quiescent 
state  of  the  gland.  Rauber  found  in  the  glands  of  pregnant 
animals  that  the  blood-vessels  were  not  in  immediate  contact 
with  the  walls  of  the  secreting  vesicles,  being  separated  from 
them  by  interposed  lymph-channels.  Coyne,  Langhans,  and 
Kolessnikow  have  also  described  these  perialveolar  lymph- 
spaces.  Their  presence  is,  indeed,  readily  demonstrated  by 
injections  with  nitrate  of  silver  solutions.  In  actively  secreting 
glands  these  channels  are  sometimes  packed  with  leucocytes, 
which  also  infiltrate  the  stroma  of  the  organ. 

Lymphatics  are  plentiful  in  the  mammary  gland.  We  find 
them  subcutaneously,  as  well  as  deep  in  the  interior  of  the 
organ.  Coyne,  in  1874,  described  the  perialveolar  lymph- 
spaces,  already  mentioned,  for  the  human  mamma,  and  Koless- 
nikow, in  1870,  perialveolar  lymph- spaces  for  the  mammary 
gland  of  the  cow.  Langhans  succeeded  in  injecting  a  rich  net- 
work of  periacinal  lymph-vessels,  likewise  lymph-channels 
around  the  excretory  ducts  and  the  lacteal  sinuses.  The  lar- 
gest lymph-vessels  are  retro-glandular.  They  are  without 
valves.  The  lymph-vessels  of  the  nipple  resemble  those  of 
the  skin.  There  seems  to  be  no  free  communication  between 
the  lacunal  and  interstitial  spaces  of  connective  tissue  of  the 
glands,  and  the  proper  lymph-channels. 

The  principal  lymph-vessels  of  the  mamma,  both  deep  and 
superficial  branches,  proceed  to  the  glands  of  the  axilla.  But 
some  of  the  mammary  lymphatics  also  communicate,  through 
intercostal  branches,  with  the  thoracic  lymphatic  glands. 
These  are  points  worthy  of  remembrance  in  studying  the  mode 
of  dissemination  in  mammary  tumors. 

Nerves  abound  less  in  the  secreting  structure  of  the  mam- 
ma than  in  its  integumentary  apparatus.  The  majority  are  of 
spinal  origin,  although  the  sympathetic  system  is  by  no  means 
excluded  from  representation.  Branches  from  the  fourth, 
fifth,  and  sixth  intercostal  nerves — the  so-called  rami  glandu- 
lar es — accompany  the  milk-ducts,  and  ramify  within  the  organ. 
Satisfactory  evidence  concerning  the  manner  of  their  ultimate 
termination  has,  however,  not  been  hitherto  obtained.  Most 
of  the  nerves  in  the  interior  of  the  organ  belong  to  the  vascular 
or  vaso-motor  variety,  and  many  are  seen  to  accompany  the 


444 


MANUAL    OF    HISTOLOGY. 


blood-vessels.     Eckliard  has  given  the  most  elaborate  descrip- 
tion of  the  nerve-supply  of  the  human  mamma. 

Structure  of  fully  expanded  gland. — Immediately  before, 
during,  and  after  lactation,  the  mamma  appears  as  a  distinctly 
lobulated  organ,  having  a  pinkish  or  yellowish  hue,  and  resem- 
bling in  consistence  the  human  pancreas  or  salivary  gland. 

The  different  lobuli  are  made  up  of  numerous  ultimate 
acini,  having,  as  a  rule,  a  rounded,  pyriform,  or  slightly  poly- 
hedral shape.  They  are  of  nearly  uni- 
form size,  and  are  closely  placed,  being 
separated  from  one  another  by  only 
sparing  amounts  of  connective  tissue, 
and  the  capillary  vascular  channels 
therein  contained.  Elastic  fibres  and 
smooth  muscle-cells  also  occur,  though 
not  constantly,  between  the  alveoli  of 
the  lobules.  Lymphoid  elements,  as 
well  as  branched  connective-tissue  cor- 
puscles, are  always  encountered  there 
in  greater  or  less  abundance.  In  addi- 
tion to  these  elements,  large  granular 
corpuscles  containing  nuclei  are  found. 
They  are  most  numerous  along  the 
course  of  the  blood-vessels,  and  appear 
to  be  identical  with  the  so-called  plasma  cells  of  Waldeyer. 
Creighton,  however,  also  describes  similar  cells  in  the  interior 
of  the  alveoli,  and  believes  that  both  are  identical,  maintain- 
ing that  they  are  derived  from  the  acinous  epithelium. 

According  to  this  author's  description,  such  cells  are  "  not 
infrequently  seen  in  the  tissue  outside  a  lobule  in  rows  three 
or  four  deep  ;  again,  they  are  found  in  the  interfascicular  spaces 
among  thelymphoid-cells,"  that  have  been  already  mentioned. 
These  large,  granular,  and  nucleated  corpuscles  are  said  to  be 
filled  with  a  bright  yellow  or  golden  pigment.  Now,  Creighton 
has  pointed  out  that  the  periodical  subsidence  of  the  mammary 
function  is  accompanied  by  the  formation  of  much  corpuscular 
waste  material.  And  the  production  of  these  remarkable  yel- 
low cells,  which  finally  leave  the  gland  by  way  of  the  lymph- 
vessels,  is,  according  to  him,  but  a  final  phase  of  this  process. 
The  mammary  epithelium  which  paves  the  acini  has  been 
variously  described  as  consisting  of  flat  polyhedral  (Reinhard) ; 


FIG.  190.  —  Transverse  section 
through  the  terminal  vesicles  of  the 
gland  in  a  nursing  woman,  showing 
mteralveolar  capillaries.  Langer. 


THE    MAMMARY    GLAND. 


445 


cubical,  cylindrical  (Kolessnikow) ;  small  polyhedral  (Langer) ; 
and  prismatic  (Kehrer)  cells.  This  discrepancy  of  opinion  re- 
ceives its  explanation  from  the  fact  that  the  epithelial  cells 


FIG.  191.— Lobule  of  a  mamma  near  the  resting  state.    Numerous  large  pigmented  cells  within  the 
acini  and  in  the  interlobular  flbrillar  tissue.     Creighton. 

have  a  different  appearance  in  the  various  conditions  interven- 
ing between  full  activity  and  complete  rest  of  the  gland. 

Creighton  has  given  a  very  satisfactory  description  of  mam- 
mary epithelium.  He  states  that  in  the  fully  expanded  gland 
"  the  floor  of  an  acinus  in  section  is  covered  by  a  mosaic  of 
polyhedric  epithelial  cells,  usually  to  the  number  of  fifteen 
or  twenty,  while  in  the  larger  elongated 
acini  as  many  as  thirty  may  be  counted. 
The  cells  are  usually  pentagonal  or  hex- 
agonal, and  the  corners  are  sometimes 
rounded.  In  each  cell  there  is  a  central 
round  nucleus,  which  colors  brightly 
with  the  staining  fluid,  and  abroad  fringe 
of  protoplasm,  which  stains  less  deeply." 
The  nucleus  varies  in  its  relative  size, 
generally  having  a  diameter  equal  to 
about  one-third  that  of  the  entire  cell. 
"  In  a  profile  view  of  an  acinus,  the  epithelium  appears  as  a 
circlet  of  oblong  cells,  in  which  the  nucleus  at  the  centre  occu- 
pies almost  the  entire  thickness  of  the  cell.  The  mammary 
epithelial  cell  may  therefore  be  described  as  a  flattened  poly- 
hedric body,  with  a  thickness  about  one-half  of  its  breadth. 
The  substance  of  the  nucleus  is  apparently  homogeneous,  with 


FIG.  192.— Fully  expanded  aci- 
nus, showing  mosaic  of  polyhedral 
cells.  Creighton. 


446 


MANUAL    OF    HISTOLOGY. 


a  deeper  line  of  staining  round  the  margin  ;  a  nucleolus  is  not 
always  prominently  seen." 

Structure  of  involuted  mamma.  —  Having  thus  briefly  indi- 
cated the  main  histological  features  of  a  fully  evolved  gland, 
we  are  now  prepared  to  examine  the  mamma  in  a  condition  of 
advanced  involution.  By  involution,  in  this  sense,  is  meant 
the  periodical  return  to  inactivity,  and  not  to  final  retrograde 
metamorphosis,  which  culminates  in  complete  senile  atrophy. 
The  glandular  lobules,  then,  in  the  involuted  organ  are  again 
found  to  be  composed  of  closely  crowded  alveoli.  But  all  the 
lobules  appear  to  have  become  smaller,  and 
their  acinous  components  are  likewise  shrunk- 
en. The  basement-membrane  of  the  latter 
does  not  appear  to  be  materially  altered,  but 
its  cellular  contents  are  considerably  changed. 
In  place  of  the  beautiful  mosaic  characteristic 
of  the  active  gland,  there  now  appears  only 
an  aggregation  of  nucleated  corpuscles  to  the 
number  of  five  or  ten.  Creighton  describes 
them  as  "  nothing  else  than  a  somewhat  ir- 
regular heap  of  naked  nuclei,  with  no  fringe 
of  protoplasm  round  them,  and  in  size  little, 
if  at  all,  larger  than  the  nucleus  alone  of  the 
P^fect  epithelium."  '  This  description,  how- 
ever>  applies  only  to  hardened  specimens,  for 
in  fresh  preparations  the  nuclei,  as  a  rule, 
show  a  broader  or  narrower  surrounding  zone  of  protoplasm. 
As  regards  the  diameter  of  the  involuted  acini,  it  is  about  one- 
fourth  that  of  the  actively  secreting  alveoli. 

Owing  to  the  shrinkage  in  the  glandular  parenchyma,  the 
blood-vessels  and  excretory  ducts,  as  already  stated,  are  more 
prominent  in  an  involuted  than  in  an  active  gland. 

It  is  not  our  purpose  here  to  trace,  step  by  step,  the  various 
processes  by  which  a  gland  passes  from  the  resting  state  to 
that  condition  of  complete  evolution  which  is  alone  compatible 
with  active  secretion.  For  the  details  of  this  interesting  subject, 
the  reader  is  referred  to  the  work  of  Creighton.  We  may,  how- 
ever, very  briefly  summarize  this  author's  account  of  the  trans- 
formations in  question.  The  one  essential  circumstance  char- 
acterizing the  whole  change  is  a  process  of  vacuolation,  which 
Creighton  assumes  to  take  place  in  the  secreting  cells.  "The 


THE    MAMMARY    GLAND.  447 

most  definite  and  unmistakable  form  of  vacuolation  is  the  sig- 
net-ring type."  This  process  is,  according  to  him,  a  true  one 
of  endogenous  cell  formation,  resulting  in  this  instance  in  the 
formation  of  milk.  Moreover,  large,  granular,  nucleated  cells, 
filled  with  a  bright  yellow  or  golden  pigment,  "found  both 
within  the  alveoli  and  in  the  interfibrillar  spaces  without  them" 


FIG.  194.— Vacnolation  of  alveolar  epithelium.  From  the  udder  of  a  ewe  shortly  after  the  end  of  lac- 
tation. The  cells  in  situ  are  vacuolated  cells,  with  the  usual  thin  and,  for  the  most  part,  uncolored  hoop 
or  ring  of  the  vacuole,  and  the  deeply  stained  peripheral  mass.  Creighton. 

characterize  the  last  stage  of  involution,  "and  the  pigment 
that  belongs  to  them  is  to  be  found  strewn  over  the  lobules 
that  have  reached  the  resting  state."  Finally,  Creighton  as- 
serts that  "  the  various  forms  of  cells  that  characterize  the 
various  stages  of  involution  must  have  resulted  from  a  trans- 
formation de  novo  of  the  renewed  epithelium,  and  not  from 
successive  changes  upon  the  same  cell."  Each  epithelial  cell, 
therefore,  that  is  used  up  in  the  formation  of  milk,  has  been  at 
one  time  a  perfect  polyhedral  corpuscle  or  fully  equipped  cell, 
and  "has  rapidly  undergone  the  cycle  of  changes  whereby 
its  whole  substance  has  been  converted  into  milk." 

A  distinguishing  feature  of  one  stage  of  evolution  which 


448 


MANUAL    OF   HISTOLOGY. 


deserves  to  be  mentioned,  is  "  the  presence  in  the  cavities  of 
the  acini  of  a  peculiar  granular  material,  the  coagulated  con- 
dition of  a  fluid."  Partsch  has  also  described  the  occurrence 
of  this  granular  mass  within  the  alveoli,  and  he  states  that  the 
secreting  epithelia,  though  of  normal  size,  were  furnished  with 
shrunken  nuclei,  and  showed  numerous  light  spots,  as  if  the 

cells  were  perforated  and  sieve-like.  It 
would  appear  that  this  writer  has  ob- 
served the  stage  of  vacuolation  with- 
out, however,  interpreting  the  same  in 
Creighton's  sense. 

Creighton  also  describes  in  certain 
glands  the  connective-tissue  stroma  as 
crowded  with  cellular  elements,  which 
he  considers  equally  with  the  pigmented 
corpuscles  as  waste-cells  of  the  secre- 
tion. Others  (Winkler,  Brunn,  and  par- 
ticularly Rauber)  have  assigned  a  far 
different  significance  to  these  bodies,  as 
will  appear  farther  on.  Finally,  Creigh- 
ton explains  that  the  secretion  of  the 
mammary  gland  "  may  be  said  to  be  pro- 
duced by  a  transformation  of  the  sub- 
stance of  successive  generations  of 

epithelial  cells,  and  in  the  state  of  full  activity  that  transfor- 
mation of  the  substance  is  so  complete,  that  it  may  be  called  a 
deliquescence." 

Although  Creighton's  investigations  did  not  extend  to  the 
human  mammary  gland,  there  is  ample  ground  for  the  belief 
that  changes  of  evolution  and  involution  similar  to  those  which 
he  has  described  in  animals,  constantly  take  place  in  the  hu- 
man female  as  well.  And  even  if  we  accept  only  some  of  his 
views  on  the  inter-relations  of  physiological  action  and  histo- 
logical  appearance,  the  discrepancy  still  existing  in  the  de- 
scriptions given  by  different  authors  will  receive  a  more  rational 
explanation  than  has  hitherto  been  offered  by  writers  on  this 
subject.  Certainly  some  of  his  assertions  appear  rather  fanci- 
ful in  their  far-reaching  novelty,  nevertheless  they  deserve  the 
attentive  consideration  which  we  have,  at  least,  in  part  bestowed 
on  them. 

From  the  results  of  our  own  examinations,  we  are  unable 


FIG.  195.— Acini  from  a  partly 
expanded  gland,  some  of  them 
filled  with  a  granular  material. 
From  the  mamma  of  a  pregnant 
cat.  Creighton. 


THE   MAMMARY    GLAND.  449 

to  concede  in  all  respects  the  correctness  of  Creighton's  inter- 
pretations. The  evidences  of  epithelial  destruction  for  purposes 
of  milk  secretion,  are  not  positive  and  convincing.  In  the  Har- 
derian  gland,  as  well  as  in  the  mamma,  we  have  observed  the 
extrusion  of  fat-droplets  from  cells  replete  with  them  without 
destruction  of  the  cell  itself.  Partsch  agrees  with  us  in  assum- 
ing that  the  cells  may  burst  or  otherwise  discharge  their  con- 
tents, and  yet  retain  enough  protoplasm  to  maintain  their  vital- 
ity ;  and  also  that  the  vital  contractions  of  the  protoplasm 
may  force  out  the  oil-globules  without  destruction  of  the  epi- 
thelium. What  Creighton  has  called  vacuolation  does  not  mean 
death  to  the  cells  concerned  in  this  action,  for  they  retain  their 
nuclei  and  sufficient  protoplasm  to  become  re-established  as 
perfect  epithelia.  That  this  reformation  of  old  epithelium 
takes  place,  is  proven  by  the  fact  that  a  new  formation  by 
proliferation  has  never  been  observed,  and  by  the  additional 
circumstance  that  the  mammary  acini  never  show  more  than 
a  single  layer  of  lining-corpuscles,  and,  moreover,  always  show 
this  layer  complete. 

In  this,  as  in  many  other  respects,  the  mamma  closely  re- 
sembles the  Harderian  gland,  more  particularly  of  the  roden- 
tia,  as  described  by  one  of  the  writers  in  a  monograph.  The 
basement-membrane  of  the  acini  in  every  particular  also  corre- 
sponds in  the  two  kinds  of  glands,  being  in  both  a  homoge- 
neous, apparently  structureless  membrane,  with  superimposed 
branched  adventitial  cells,  the  so-called  Stutzzellen  of  German 
writers.  A  basket-shaped  reticulum,  such  as  has  been  described 
by  Boll,  Langer,  Kolessnikow,  Moullin,  and  others,  is  never 
found  to  constitute  this  membrana  propria,  although  artifi- 
cially, appearances  simulating  a  structure  of  this  kind  are 
readily  obtained,  and  have  been  interpreted  by  several  histolo- 
gists  as  natural  occurrences. 

In  the  cutaneous  sebaceous  glands  the  secreting  vesicles  are 
filled  with  several  superimposed  layers  of  epithelia,  and  it  is 
this  circumstance  which  leads  to  an  entirely  different  mode 
of  secretion.  For  there  it  would  indeed  appear  that  the  cells 
undergoing  fatty  degeneration  become  detached  from  their 
bases  and  find  their  way  into  the  narrow  lumen  of  the  acinus. 
The  older  or  inner  generation  of  cells  thus  vanishing  is  replaced 
by  new  corpuscles  formed  by  gradual  proliferation  from  the 
peripheral  zone. 


450  MANUAL   OF  HISTOLOGY. 

RaiCber*  s  mews  on  the  mamma  and  the  lacteal  secretion  are 
somewhat  startling,  but  must  occupy  our  attention  here.  From 
a  series  of  very  carefully  conducted  examinations,  principally 
on  the  glands  of  guinea-pigs  during  and  after  pregnancy,  he 
feels  justified  in  concluding  that  milk  owes  its  orgin  to  the 
entrance  of  countless  leucocytes  into  the  lumen  of  the  gland- 
vesicles.  The  emigrated  lymphoid  elements,  he  believes,  pene- 
trate the  alveolar  walls,  passing  through  the  single  layer  of 
epithelial  cells  which  line  them.  Arrived  in  the  interior  of  an 
ultimate  acinus,  the  leucocytes  undergo  fatty  metamorphosis, 
and  thus  at  length  furnish  the  most  essential  and  characteristic 
ingredient  of  milk,  viz.,  the  milk-globules.  Rauber,  therefore, 
discards  the  notion  that  the  formed  particles  of  the  lacteal 
secretion  originate  in  the  glandular  epithelium,  and  represent 
the  elaborated  products  of  its  functional  activity.  He  also 
denies  that  previously  formed  milk  globules,  or  colostrum  cor- 
puscles, ever  pass  through  the  alveolar  walls.  Thus  the  prim- 
itive opinion  advanced  by  Empedocles,  describing  milk  as  white 
pus,  is  in  a  measure  revived,  and  milk  is  held  to  be  directly 
-derived  from  the  white  corpuscles  of  the  blood. 

Preparations  of  mammary  glands  taken  from  animals  still 
•suckling  their  young,  according  to  him,  invariably  show  the 
intraglandular  lymph-vessels  replete  with  leucocytes,  the  stro- 
ma  similarly  infiltrated,  identical  corpuscles  in  greater  or  less 
abundance  within  the  vesicles,  and  transitional  forms  between 
lymphoid-corpuscles  and  milk-globules.  These  claims,  granted 
to  be  facts,  and  considered  in  conjunction  with  the  circum- 
. stance  that  epithelial  proliferation  is  not  seen,  would  certainly 
.go  far  to  make  Rauber's  theory  seem  a  somewhat  plausible 
one.  Nevertheless,  we  require  corroborative  evidence  from 
Bothers,  before  his  views  can  be  accepted  as  anything  more  than 
an  ingenious  hypothesis. 

Rauber  has  also  described  the  occurrence  of  a  delicate  stri- 
.ation  within  the  epithelial  cells  of  the  alveoli.  These  striae  are 
said  to  be  in  all  respects  similar  to  those  found  in  the  secreting 
elements  of  certain  portions  of  the  salivary  glands  and  the 
iubules  of  the  kidneys. 

As  regards  the  corpuscles  of  Donne,  or  colostrum  bodies, 
most  authors  regard  them  as  the  products  of  desquamation  of 
the  alveolar  epithelium,  the  latter  being  in  a  condition  of  fatty 
degeneration  (Winkler,  De  Sinety,  Buchholtz,  and  others). 


THE    MAMMARY    GLAND.  451 

Some  histologists,  like  Strieker,  hold  that  oil-globules  may  be 
expelled  from  the  interior  of  fat-filled  cells  without  disintegra- 
tion of  their  protoplasmic  bodies.  It  is  an  undoubtable  fact 
that  colostrum  corpuscles,  when  managed  with  proper  precau- 
tions, may  be  seen  to  yield  droplets  of  fat  under  the  micro- 
scope, just  as  amoebae  reject  similar  contained  particles.  Rau- 
ber,  however,  maintains  that  these  bodies  represent  leucocytes 
in  various  stages  of  fatty  metamorphosis,  and  he  calls  such 
corpuscles,  when  found  in  the  gland  vesicles,  galactoblasts. 

In  the  gland  of  Harder,  one  of  the  writers  has  found  the 
spacious  gland  vesicles  lined  with  very  large  epithelia ;  and 
these  cells  were  in  many  animals  entirely  fat-filled.  They  se- 
creted a  greasy  substance  not  unlike  thick  milk.  Yet  destruc- 
tion of  the  cell-body  did  not  occur,  at  least  evidences  of  such 
a  process  could  not  be  obtained.  Partsch  has  therefore  antici- 
pated the  authors  in  their  conclusion  that  the  secretion  of  milk 
is  accomplished  in  much  the  same  way  in  which  the  creamy  pro- 
ducts of  the  Harderian  gland  are  formed,  i.e.,  without  total 
destruction  of  epithelial  cells.  According  to  our  view,  then, 
and  it  nearly  coincides  with  the  opinion  of  Strieker,  Winkler, 
and  especially  Partsch,  the  cells  containing  the  fat-globules 
may,  indeed,  burst  and  discharge  their  contents,  but  the  nu- 
cleus and  sufficient  protoplasm  are  retained  to  enable  the  epi- 
thelium to  recuperate,  and  in  the  course  of  time  again  and 
again  discharge  its  contents.  Along  with  this  mode  of  milk 
secretion,  a  second  process  occurs.  This  consists  of  the  gradual 
extrusion  of  oil-droplets,  the  cell  body  remaining  entirely  in- 
tact, since  the  mere  vital  contractions  of  the  protoplasm  suf- 
fice to  drive  out  one  milk-globule  after  another. 

When  the  activity  of  the  gland  is  suddenly  heightened  in 
the  period  immediately  before  childbirth,  some  few  epithelial 
cells  are  desquamated.  These,  appearing  in  the  milk  of  most 
women,  are  identical  with  the  bodies  known  and  described  as 
colostrum  corpuscles. 

Of  other  anatomical  constituents  of  normal  milk,  we  only 
find  the  milk-  or  oil-globules.  They  are  suspended  in  the  fluid 
emulsion  which  milk  truly  represents,  in  countless  numbers. 
They  vary  in  size  from  0.002  to  0.009  mm.  A  very  delicate 
fringe  of  protoplasm  adheres  to  their  periphery,  and  it  is  for 
this  reason  that  they  may  appear  to  become  stained  when  sub- 
mitted to  the  action  of  proper  dyes. 


452 


MANUAL    OF    HISTOLOGY. 


DEVELOPMENT   OF  THE   GLAND. 


Like  the  other  cutaneous  glands  of  the  body,  the  mamma 
is  first  formed  by  a  proliferation  inward  of  certain  epidermal 
cells.  In  other  words,  the  breast  results  from  a  downward 
extension  of  epiblastic  corpuscles.  The  first  unmistakable  indi- 
cation of  the  future  gland  is  seen  about  the  third  or  fourth  month 
of  pregnancy.  At  that  time  it  consists  of  a  solid  plug,  or  pro- 


Fio.  196.— 1.  Rudimentary  form  of  gland 
in  human  fcetus:  a,  6,  epidermis :  c,  aggrega- 
tion of  cells  ;  d,  connective  tissue  layer.  2.  From 
a  seven-months'  foetus  :  a,  central  substance  ; 
&,  larger,  and  c,  smaller  outgrowths.  Frey. 


FIG.  197.— Embryonal  mamma :  a,  cen- 
tral mass,  with  6,  and  c,  variously  shaped 
outgrowths.  Frey. 


cess,  extending  downward  from  the  rete-mucosum  of  the  skin. 
This  has  been  called  Drusenfeld,  by  Huss.  From  the  internal 
end  of  this  solid  process,  sprouts,  or  offshoots,  are  developed, 
and  they  represent  the  future  separate  glands  constituting  the 
mature  organ.  These  buds  have  a  pyrif  orm,  or  club-like  shape, 
and  are  surrounded  by  ordinary  embryonal  connective  tissue. 
The  further  growth  of  the  gland  takes  place  by  a  process  of 
continuous  extension  and  subdivision,  but  indications  of  the 
latter  are  not  always  found  at  birth.  Ducts  are  already  visible 
in  the  new-born  infant,  but  the  aggregations  of  cells  represent- 
ing the  future  acini,  remain  without  lumina  for  a  much  longer 
period. 

Th.  Kolliker  describes  as  a  constant  occurrence,  especially 
marked  in  the  breasts  of  female  infants,  the  dilatation  of  a 
greater  or  smaller  number  of  milk-ducts.  Such  ectatic-canals 


DEVELOPMENT  OF  THE  GLAND.  453 

liave  their  lumina  filled  with  desquamated  epithelial  cells,  and 
a  whitish,  granular  material.  Formerly,  these  occurrences  were 
considered  to  be  exceptional,  and  were  regarded  as  having  a 
pathological  significance.  During  the  first  year  of  extra-uterine 
life,  this  characteristic  process  of  progressive  dilatation  may 
assume  such  large  dimensions,  that  the  mamma  may  come  to 
resemble  cavernous  tissue,  the  ectatic  spaces  of  which  are 
paved  with  flattened  epithelium.  Within  certain  limits,  Kolli- 
ker  regards  this  as  a  perfectly  normal  physiological  event.  But 
he  adds  that  an  exaggerated  process  of  this  kind  may  result  in 
early  mastitis.  Such  an  occurrence,  he  thinks,  may  explain 
the  rudimentary  development  of  the  breasts  observed  in  some 
women  of  otherwise  normal  growth. 

The  post-embryonal  growth  of  the  mamma  has  been  care- 
fully studied  by  Langer,  and  his  results  and  conclusions  having 
been  confirmed  by  the  investiga- 
tions of  Kolliker,  Huss,  and  others, 
must  still  be  received  as  represent- 
ing the  true  condition  of  things,  in 
spite  of  the  novel  and  heterodox 
views  advanced  by  Creighton. 

Up  to  the  time  of  puberty,  the 
growth  of  the  breast  is  very  grad- 
ual and  quite  insignificant,  even  in 
females.  Then,  however,  the  ducts 
begin  to  rapidly  ramify  in  all  di- 
rections, and,  by  offshoots  from  va- 
rious points,  true  acini  are  at  length 
developed.  But  they  remain  of 
small  size  until  the  stimulus  of 
pregnancy  causes  a  further  evolution.  In  the  male,  the  exist- 
ing ducts,  as  a  rule,  atrophy  with  advancing  age.  The  evolu- 
tion changes  which  the  mamma  undergoes  during  pregnancy, 
have  already  been  set  forth,  and  there  remain  to  be  considered 
only  those  final  phases  of  metamorphosis  which  take  place  in 
the  climacteric  period  of  life. 

These  are  readily  understood,  consisting  essentially  of  a 
complete  atrophy  of  all  the  secreting  acini.  Simultaneously 
with  these  atrophic  changes  the  epithelia  of  the  galactophorous 
ducts  become  flattened,  and  finally  shrink,  so  as  to  form  only 
squamous  plates,  which  line  the  ramifying  processes  of  connec- 


454  MANUAL    OF    HISTOLOGY. 

tive  tissue  representing  the  former  lactiferous  canals.  The 
terminal  portions  of  these  larger  duct-remnants  are  sometimes 
connected  with  minute  channels,  the  latter  being  the  remnants 
of  collapsed  smaller  ducts.  In  some  measure  we  find  a  com- 
pensatory production  of  fat,  which  partly  replaces  the  faded 
acini.  The  breasts  of  old  women,  therefore,  consist  of  fibrous 
tissue,  with  a  large  proportion  of  elastic  elements,  fat-cells,  and 
the  remnants  of  the  ducts.  It  may  be  remarked  that  the  latter 
frequently  show  cystic  dilatations,  the  cavities  being  filled  with 
a  dirty,  slimy  fluid.  The  blood  and  lymph-vessels,  but  especi- 
ally the  latter,  participate  in  the  general  atrophy  of  the  tissues. 

This  succinct  account  concerning  the  histogenesis  of  the 
mammary  gland,  does  not,  as  already  intimated,  represent  the 
unchallenged  opinion  on  its  first  development.  For  Creighton, 
in  the  remarkable  work  already  cited,  radically  opposes  the 
view  that  the  mamma  takes  its  origin  from  the  epiblast.  He 
believes,  on  the  contrary,  that  it  starts  from  the  mesoblast,  or 
connective-tissue  layer  of  the  embryo,  and  not  the  upper  epi- 
thelial layer  or  epiblast.  According  to  him,  moreover,  and  his 
conclusions  are  based  on  developmental  studies,  chiefly  of  the 
guinea-pig's  gland,  the  process  may  be  justly  described  as  a 
centripetal  one,  whereas  the  current  view  represents  this  gland- 
develpoment  as  essentially  centrifugal.  We  have  already  ex- 
pressed our  adherence  to  the  current  view,  attributing  this 
growth  to  extension  from  a  central  point.  Nevertheless,  it 
seems  proper  to  briefly  give  the  conclusions  of  Creighton,  es- 
pecially since  they  appear  to  be  singularly  corroborative  of  the 
account  given  by  Goodsir  of  this  process,  as  early  as  1842,  an 
account  which  has  apparently  remained  almost  unnoticed  by 
workers  in  this  branch  of  scientific  medicine. 
,  Creighton  then  concludes  his  inquiry  as  follows  : 

"  1.  The  mammary  acini  of  the  guinea-pig  develop  at  many 
separate  points  in  a  matrix -tissue.  The  embryo  cells  from 
which  they  develop  are  of  the  same  kind  that  give  origin  to 
the  surrounding  fat-tissue.  The  process  of  development  of  the 
mammary  acini  is,  step-for-step,  the  same  as  that  of  the  fat- 
lobules." 

"  2.  The  ducts  of  the  mamma  develop  from  the  same  matrix- 
tissue,  by  direct  aggregation  of  the  embryonic-cells,  along 
predetermined  lines.  The  ducts  develop,  in  the  individual 
guinea-pig,  before  the  acini,  whereas,  in  the  phylogenetic  sue- 


DEVELOPMENT  OF  THE  GLAND.  455 

cession,  the  ducts  are  a  later  acquisition.  This  reversal  of  the 
order  of  acquisition  of  parts  is  in  accordance  with  the  prin- 
ciple stated  by  Herbert  Spencer,  that  'under  certain  circum- 
stances the  direct  mode  of  development  tends  to  be  substituted 
for  the  indirect.' ' 

Hints  regarding  the  histological  study  of  the  mamma. — 
The  evolution  of  the  mammary  structure  progresses  paripassu 
with  the  development  of  its  functional  activity.  It  is  the  stim- 
ulus of  pregnancy  which  determines  both.  Nevertheless, 
even  during  the  period  of  its  fullest  physiological  bloom,  i.e., 
during  lactation,  variations  in  the  degree  of  functional  activity 
normally  take  place.  Moreover,  the  same  gland  may  contain 
lobules  which  are  comparatively  at  rest,  and  others  which  are 
at  the  full  height  of  activity.  This  should  always  be  borne  in 
mind  in  interpreting  the  results  of  histological  inspection  of 
this  organ,  lest  erroneous  impressions  be  conveyed. 

The  alveolar  epithelial  cells  will,  therefore,  not  be  found 
alike  in  the  different  acini,  nor  yet  even  in  the  same  vesicle. 
We  may  find  cuboidal  cells,  and  cylindrical  ones,  and  flattened 
corpuscles,  and  in  addition,  various  transitional  forms  between 
these  types. 

The  nucleus  will  appear  round,  or  oval,  and  about  6-7  j*  in 
diameter.  Sometimes  two  nuclei  may  be  found  in  one  cell. 
The  radiating  striation  observed  by  Rauber  in  many  cells,  has 
already  received  mention.  It  is  a  noteworthy  fact  that  the 
cells  themselves  contain  only  a  very  small  proportion  of  fatty 
granules,  whereas  the  intra-alveolar  lumen  is  often  replete 
with  the  same. 

In  order,  then,  to  study  the  histology  of  the  gland  at  the 
high- water-mark  of  its  functional  activity,  animals  should  be 
chosen  which  have  either  just  given  birth  to  their  young, 
or  are  about  to  do  so.  For  the  normal  conditions  of  the 
human  mamma  are  rapidly  transformed  by  post-mortem  change, 
if  not  previously  altered  in  consequence  of  the  disease  which 
caused  the  death  of  the  individual.  The  organ  may  be  exam- 
ined fresh,  or  else  hardened  and  then  cut  in  sections  to  be 
stained  and  mounted  in  the  ordinary  manner. 


456  MANUAL    OF    HISTOLOGY. 


BIBLIOGRAPHY. 

RUDOLFI.     Bemerkungen  ueber  den  Bau  der  Briiste.      Abhandl.  der  Berliner  Akad. 

1831. 

DONNE,  AL.     Du  lait,  etc.,  en  particulier  de  celui  des  nourrices.     Paris,  1837. 
COOPER.     Anatomy  of  the  Breast.     1839. 

GUTERBOCK.     Ueber  die  Donneschen  Corps  granuleux.     Miiller's  Archiv.     1839. 
HENLE.     Ueber  die  mikroskop.  Bestandth.  d.  Milch.   Froriep's  Notizen.     1839. 
FETZER.     Ueber  die  weiblichen  Briiste.     Wiirzburg,  1840. 
NASSE.     Ueber  die  mikroskopischen  Bestandtheile  der  Milch.     Miiller's  Archiv. 

1840. 

GOODSIR.     Anatom.  and  Pathol.  Observations.     1845. 
REINHARDT.     Ueber  die  Entstehung  der  Kornchenzellen.   Virchow's  Archiv.    Vol.  I. 

1847. 

WILL.     Ueber  die  Milchabsonderung.     Erlangen,  1850. 
LANGER.     Ueber  den  Bau  und  die  Entwickelung  der  Milchdriise.      Denkschr.  d. 

Wien.  Akad.     1851.     Also  article  on  the  Mammary  Gland,  in  Strieker's  His- 
tology. 

LUSCHKA.     Zur  Anatomic  der  Mannl.  Brustdriisen.     Miiller's  Archiv.     1852. 
ECKHARD.     Beitr.  zur  Anat.  u.  Phys.  1.  Band.     1.  Heft.     Giessen,  1855. 
VIRCHOW.     Die  Cellularpathologie,  p.  305.     1859. 
DUVAL.     Du  mamelon  et  de  son  aureole.     Paris,  1861. 
GRUBER.     Ueber  die   Mannliche   Brustdriise.     Memoiren  d.    Petersburger   Akad. 

1866. 
STRICKER.     Ueber  contractile  Korper,  etc.     Sitzber.  d.  Akad.  Wien.     Vol.  LIII. 

1866. 

ZOCHER.     Beitr.  zur  Anat.  u.  Phys.  d.  weibl.  Brust.     Leipzig,  1869. 
HENNIG.     Beitrag.  zur  Morphologic  der  weibl.  Milchdriise.    Arch.  f.  Gynakol.    Vol. 

II.,  p.  331.     1871. 
Huss.     Beitriige  zur  Entwickelung  der  Milchdriise  beim  Menschen,  etc.     Jenaische 

Zeitschrift,  Vol.  VII.,  2.     1873. 
LANGHANS.     Die  Lymphgefasse  der  Brustdriisen  in  ihren  Beziehungen  zum  Krebse. 

Arch,  fiir  Gynakologie,  Bd.  VIII.,  S.  181.     1875.     Also,  Zur  pathologischen 

Histologie  der  weiblichen  Brustdriise.  Virchow's  Archiv,  p.  132.   Bd.  58.   1873, 
COYNE.     Sur  les  lacunes  lymphatiques  de  la  glande  mammaire.     Soc.  de  Biologic. 

21.  Nov.,  1874.     Also,  Sur  les  lacunes  lymphatiques  de  la  glande  mammaire. 

Gazette  Hebdom.,  p.  775.     1874. 

DE  SINETY.     Eecherches  sur  les  globules  du  lait.     Arch,  de  Phys.     1874. 
VON  BRUNN.     Gottinger  Nachrichten,  No.  19.     1874. 
LABBE  and  COYNE.     Traite  des  tumeurs  benignes  du  sein.     1876. 
BUCHHOLTZ.     Das  Verhalten  der  Colostrumkorper,  etc.     Gottingen,  1877. 
DE  SINETY.     Sur  le  develop,  et  1'histol.  comp.  de  la  mamelle.     Gaz.  med.  de  Paris, 

No.  6,  p.  68.     1877. 
KOLESSNIKOW.     Die  Histologie  der  Milchdriise  der  Kuh.  Virchow's  Archiv.    Bd.  70, 

p.  531.     1877. 

SCHMID,  H.     Zur  Lehre  von  der  Milchsecretion.     Wiirzburg,  1877. 
WENDT.     Ueber  die  Hardersche  Driise  der  Saugethiere.     Strassburg,  1877. 
WINKLER.     Bau  der  Milchdriise.     Jahresber.  d.  Ges.  f .  Natur.  u.  Heilkunde.     Dres- 


BIBLIOGRAPHY.  457 

den,  1874.  Beitr.  zur  Histol  u.  Nervenverth.  in  d.  Mamma.  Archiv  f.  Gyna- 
kol.  Vol.  XI.  1877. 

KOLLIKER,  TH.  Beitrage  zur  Kenntniss  der  Brustdriise.  Verh.  d.  phys.-med.  Ges. 
zu  Wiirzburg.  1879. 

RAUBER.  Ueber  die  Absonderung  der  Milch.  Sitzber.  d.  naturf .  Gesel.  zu  Leip- 
zig, pp.  30-34.  1879.  Also,  Bemerkungen  ueber  den  feineren  Bau  der  Milch- 
druse.  Schmidt's  Jahrb.  1879. 

RAUBEII.     Ueber  den  Ursprung  der  Milch.     Leipzig,  1879. 

BILLROTH.  Die  Krankheiten  der  Brustdriisen.  Deutsche  Chirurgie.  Lieferung 
41.  1880. 

PARTSCH.     Ueber  den  feineren  Bau  der  Milchdriise.     Breslau,  1880. 

MOULLIN.  The  Membrana  Propria  of  the  Mammary  Gland.  Journ.  of  Anat.  and 
Phys.  April,  1881. 

See  also  the  text-books  of  Sharpey  and  Quain,  Frey,  Kolliker,  Krause,  and  Sappey. 


INDEX. 


ACINI  of  expanded  mamma,  444 
of  liver,  183 
of  lung,  260 
of  pancreas,  410 
Adenoid  tissue,  69 

of  lymph-glands,  178 
Adventitia  of  capillaries,  148 

of  arteries,  151,  155 
Afferent  vessels  of  kidney,  206 
Aglobulie  intense,  38 
Air-cells  of  lung,  260 
Alcohol  and  acetic  and  muriatic  acids,  15 

and  acetic  acid  mixture,  14,  15 
ALIMENTARY   CANAL,  386 
general  considerations,  386 
LARGE  INTESTINE,  400 
blood-vessels  of,  401 
lymphatics  of,  401 
ne?ves  of,  401 
structure  of,  400 
(ESOPHAGUS,  386 

blood-vessels  of,  388 
fibrous  envelope  of,  388 
layers  of,  386 
lymphatics  of,  388 
mucous  membrane  of,  386 
muscular  coat  of,  387 
muscularis  mucosse  of,  387 
nerves  of,  388 
submucous  layer  of,  387 
RECTUM,  401 

sphincter  ani  of,  401 
structure  of,  401 
SMALL  INTESTINE,  394 
blood-vessels  of,  399 
Brunner's  glands  of,  397 
corona  tubulorum  of,  396 
follicles  of  Lieberkiihn  of,  398 
glands  of,  396 
lymphatics  of,  399 


ALIMENTARY  CANAL- 
SMALL  INTESTINE — 

mucous  membrane  of,  395 
muscular  coat  of,  394 
muscularis  mucosse  of,  396 
nerves  of,  399 

plexus  of  Auerbach,  399 
plexus  of  Meissner,  399 
Peyer's  patches  of,  396 
serous  coat  of,  394 
solitary  follicles  of,  396 
submucous  layer  of,  396 
valvulse  conniventes  of,  395 
villi  of,  395 
STOMACH,  388 

blood-vessels  of,  392 
compound  peptic  glands  of,  390 
etat  mamelonne  of,  389 
lymphatics  of,  393 
mucous  membrane  of,  389 
muscular  coat  of,  388 
muscularis  mucosss  of,  389 
nerves  of,  393 
peptic  glands  of,  389 
pyloric  glands  of,  391 
serous  covering  of,  388 
submucous  layer  of,  389 
VERMIFORM  APPENDIX,  401 

Alizarine,  28 

Alum  carmine,  27 

Alveoli  of  lung,  260 

Ammonia  bichromate,  14 

Amoeboid  movement,  39,  40 

Anastomosis  of  capillaries,  148 

Angle  of  aperture,  11 
of  lenses,  10 

Aperture,  angle  of,  11 

Apparatus,     general,    for    microscopical 
work,  1,  2,  3,  4 

Appendix  vermiformis,  401 


460 


INDEX. 


Arachnoid,  spinal,  297 

Archil,  staining  with  French,  28 

Arciform    fibres   of    medulla    oblongata 

394 

Areola  of  mamma,  442 
Arnold's  borax  carmine  staining,  22 
Arrangement  of  object,  6 
Arteria  centralis  retinae,  347 

hyaloidea,  349 
Arteries,  152 
Arterioles,  152 
Auerbach,  intercalated  areas  of,  147 

plexus  of,  123,  399 
Auricle  of  ear,  353 
Axis-cylinder  of  nerve-fibres,  110 

D ARTHOLINB,  glands  of,  241 
J-*    Beale,  spiral  fibre  of,  122 
Bed  of  nail,  294 
BIBLIOGRAPHY — 

of  alimentary  canal,  402 

of  blood,  54 

of  blood-vessels,  161 

of  bone,  101 

of  brain,  326 

of  cartilage,  88 

of  central  nervous  system,  326 

of  cerebellum,  326 

of  connective  substances,  81 

of  ear,  367 

of  epithelium,  61 

of  eye,  352 

of  female  organs  of  generation,  251 

of  general  methods,  32 

of  kidney,  222 

of  liver,  199 

of  lymphatic  system,  182 

of  male  organs  of  generation,  238 

of  mammary  gland,  456 

of  mouth  and  tongue,  384 

of  muscle,  140 

of  nasal  fossae,  pharynx,  and  tonsils, 
375 

of  nervous  system,  127 

of  pancreas,  418 

of  pituitary  body,  419 

of  respiratory  tract,  267 

of  skin,  295 

of  spinal  cord,  325 

of  spleen,  418 


BIBLIOGRAPHY — 
of  teeth,  108 
of  thymus  gland,  419 
of  thyroid  body,  419 
of  urinary  excretory  passages  and  su- 
prarenal capsules,  437 
Bichromate  of  ammonia,  14 

preparation  of  nerves  with,  115 
Bichromate  of  potassium,  14 
Bigelow's  studies  on  cartilage,  87 
Bile-ducts,  191 
Bismark  brown,  26 
Bladder,  430 
BLOOD,  34 

amoeboid   movements   of    leucocytes 

of,  39 
Brownian  movement  in  leucocytes  of, 

39 
circulation  of,  examined  during  life, 

45 

curara  for  paralysis  of  frogs,  45 
globules  of,  in  different  fluids,  38 
granules  of,  39 
haematoblasts  of,  47 
heating  slide  for  the  study  of,  40 
liquor  sanguinis,  or  plasma  of,  34 
red  corpuscles  of,  34 

action  of  acids  on,  43 
of  alkalies  on,  44 
of  carbonic  acid  dn,  42 
of  distilled  water  on,  41 
of  electricity  on,  44 
of  salt  solution  on,  40 
counting  of,  48,  53 
crenation  of,  45 
development  of,  47 
examination  of,  47 
haemochromometer  for  estimat- 
ing richness,  53 
haemoglobin  of,  53 
internal  structure  of,  46 
Keyes's  method  of  counting,  50 
Malassez's  method  of  counting, 

50 

measurement  of,  36 
number  of,  37 
stroma  of,  46 

third  corpuscular  element  of,  48 
white  or  colorless  corpuscles  of,  48 
31ood-corpuscles,  nucleated,  95 
Blood-crystals,  53 


INDEX. 


461 


BLOOD-VESSELS,  142 

methods  of  injecting,  30 

of  bladder,  431 

of  choroid,  337 

of  cornea,  333 

of  iris,  343 

of  kidney,  213 

of  large  intestine,  401 

of  liver,  186 

of  lung,  263 

of  lymph-glands,  179 

of  mamma,  442 

of  mouth,  379 

of  oesophagus,  388 

of  optic  nerve,  349 

of  ovary,  247 

of  pancreas,  411 

of  penis,  224 

of  retina,  347 

of  skin,  279 

of  small  intestine,  399 

of  spinal  cord,  298 

of  spleen,  407 

of  stomach,  392 

of  suprarenals,  436 

of  testis,  234 

of  thymus,  414 

of  thyroid,  416 

of  uterus,  245 

ARTERIES,  151 

advent! tia  of,  151,  155 
external  elastic  coat  of,  155 
internal  elastic  coat  of,  152 
internal  fibrous  coat  of,  153 
intima  of,  152 
media  or  musculosa  of,  154 
muscular  and  elastic  types  of,  152 

ARTERIOLES,  152 

CAPILLARIES,  anastomosis  of,  148 
endothelial  desquamation,  147 
endothelium,  143 
genesis,  reproduction,  and  regen- 
eration of,  150 
intercalated  areas  of,  147 
intracellular  network,  143 
intranuclear  network,  143 
perithelium  or  adventitia  of,  148 
ramification  of,  149 
structure  of,  146 
varieties  of,  145 

COCCYGEAL  GLAND  OF  LUSCHKA,  158 


BLOOD-VESSELS- 
CORPORA  CAVERNOSA,  160 

general  remarks  on,  142 
INTERCAROTID  GLAND,  160 

lymphatics  of,  161 

nerves  of,  161 

perivascular  spaces,  161 

varieties  of,  142 

vasa  vasorum,  161 
VEINS,  155 

distinction  between  veins,   arte- 
ries, and  capillaries,  156 

internal  elastic  coat  of,  157 

internal  fibrous  coat  of,  157 

points  of    difference  from  arte- 
ries, 156 

structure  of,  156 

valves  of,  158 

venules,  156 

Boehmer's  hsematoxylon,  23 
BONE,  89 

cancellous  tissue  of,  94 
chondro-porosis,  98 
compact  tissue  of,  89 
corpuscles  of,  90 
development  of,  96,  99 
formation  of  callus  in,  100 
formation  of,  from  cartilage,  97 

from  membrane,  98 
Haversian  canals  of,  91 
Howship's  lacunae  of,  100 
intermediary  cartilage  of,  97 
lacunae  of,  91 
lamellae  of,  90 
marrow  of,  95 

cells  of,  95 

myeloplaxes,  95 

primary  cavities  of,  98 

red,  95 

yellow,  95 
metaplastic,  98 

naphthaline  yellow  for  staining,  27 
osteobtasts,  96,  98 
osteoclasts,  100 
osteoporosis,  99 
periosteal  processes  of,  94 
periosteum  of,  95 
points  of  ossification,  98 
preparation  of,  92 
Sharpey's  fibres  of,  94 
varieties  of,  89 


462 


INDEX. 


Borax  carmine,  22 

Bowman's  capsules  of  kidney,  204 

glands  of  nose,  372 

membrane,  79,  331 
Brain,  method  of  hardening,  15 
Branched  corpuscles  of  connective  tissue, 

67 

Bronchioles,  260 
Bronchi,  primary,  257 

smaller.  259 

Brownian  movement,  39 
Brunner's  glands,  397 
Burdach,  column  of,  298 

CALCIFICATION  of  cartilage,  84 

^     of  cartilages  of  larynx,  255 

Callus,  formation  of,  100 

Calyx  of  kidney,  216 

Canal,  central,  of  spinal  cord,  301 

of  Petit,  350 

of  Schlemm,  336 
Canals,  dentinal,  104 

intermediate,  of  liver,  184 

semicircular,  359 
Capillaries,  142 
Capillary  bile-ducts,  192 
Capsule,  internal,  of  brain,  317 

of  kidney,  216 

of  liver,  183 

of  spleen,  404 

of  suprarenal  bodies,  432 

of  Tenon,  337 

of  thymus,  412 

of  thyroid,  415 
Capsules,  suprarenal,  431 
Carmine,  alum,  27 
CARTILAGE,  82 

Bigelow's  studies  on,  87 

capsules  of,  82 

corpuscles  of,  82,  83 
division  of,  86 
structure  of,  87 

daughter-cells,  84 

fibrillation  of,  83 

fibrous,  86 

hyaline,  82 

calcification  of,  84 
methods  of  studying,  84 

intercellular  substance  of,  83,  87 

intermediary,  97 

parenchymatous,  83 


CARTILAGE— 

perichondrium  of,  86 
purpurine  for  staining,  85 
reticular  or  yellow  elastic,  85 
varieties  of,  82 
Spina's  views  on,  87 
Cartilages  of  bronchi,  257 

of  larynx,  254 
Cartilago-triticea  of  larynx,  253 
Caruncula  lachrymalis,  330 
Cavernous  tissue,  160 
Cells,  giant,  95 

of  liver,  189 
Cellular  tissue,  63 
Cement  of  teeth,  105 
Central  canal  of  spinal  cord,  301 
CENTRAL  NERVOUS   SYSTEM,  296 
CEREBELLUM,  317 

cells  of  Purkinje  of,  318 
corpus  dentatum  of,  317 
cortex  of,  319 
cerebral  ganglia,  319 
cerebral  ventricles,  319 
CEREBRUM,  321 
cortex  of,  321 
convolutions  of,  321 
fissure  of  Rolando,  321 

of  Sylvius,  321 
island  of  Reil,  322 
meninges  of,  321 
minute  structure  of,  323 
cortex  of,  323 

motor  tract  of  hemispheres,  322 
paracentral  lobule,  323 
choroid  plexus,  320 
corona  radiata,  317 
corpus  striatum,  319 
ependyma,  320 
internal  capsule,  317 
locus  cseruleus,  315 

niger,  316 

medulla  oblongata,  307 
arciform  fibres  of,  309 
central  gray  matter  of,  308 
decussating  fibres  of,  307 
formatio-reticularis  of,  308 
raphe  of,  307 
nucleus  lenticularis,  316 
OLIVARY  BODY,  310 

glosso-pharyngeal,  root  of,  313 
hypoglossal,  nucleus  of,  311 


INDEX. 


463 


CENTRAL  NERVOUS  SYSTEM— 
OLIVARY  BODY — 

nucleus  and    root  of    abducens 

nerve,  314 

parolivary  nucleus  of,  311 
roots  of  fifth  nerve,  315 
upper  spinal  accessory,  nucleus 

of,  311 

optic  thalami,  319 
pons,  315 

spinal  arachnoid,  297 
spinal  cord,  298 

amyelinic  fibres  of,  801 
blood-vessels  of,  298 
central  canal  of,  301 
cervical  enlargement  of,  304 
column  of  Burdach  of,  298 
column  of  Clarke  of,  304 
column  of  Goll  of,  298 
dorsal  region  of,  304 
epithelium  of,  301 
filum  terminale  of,  302 
general  histology  of,  298 
gray  commissure  of,  304 
gray  matter  of,  299 
lumbar  enlargement  of,  303 
methods  of  study  of,  305 
myelinic  fibres  of,  300 
nerve-elements  of,  299 
neuroglia-cells  of,  298 
root  radicles  of,  299 
special  study  of  different  portions 

of,  301 

white  commissure  of,  303 
white  substance  of,  299 
spinal  dura  mater,  296 
spinal  fluid,  297 
spinal  pia  mater,  297 
Cerebellum,  317 
Cerebral  ganglia,  319 
meninges,  321 
ventricles,  319 

Cervical  enlargement  of  spinal  cord,  304 
Chalice  cells,  60 
Chamber,  moist,  42 
Chloride  of  gold,  28,  29 
Chondro-porosis,  98 
Choroid  coat  of  eye,  338 

plexus,  320 
Cilia  of  eyelids,  328 
Ciliary  body,  340 


Ciliated  epithelium,  58 
Circle  of  Haller,  349 
Circulation  of  blood,  45 
Circulus  venosus  of  Haller,  442 
Clarke,  column  of,  304 
Clitoris,  240 
Coats  of  arteries,  152 
Coccygeal  gland,  158 
Cochlea,  362 

Cohnheim's  muscular  areas,  136 
Colostrum,  450 
Columnar  epithelium,  60 
Column  of  Burdach,  298 

of  Clarke,  304 

of  Goll,  298 

Columns,  muscular,  138 
Commissure,  gray,  of  spinal  cord,  304 

white,  of  spinal  cord,  303 
Conjunctiva,  330 

fornicis,  329 

tarsi,  328 
CONNECTIVE  SUBSTANCES,  62 

branched  corpuscles  of,  67 

corpuscles  of,  65 

development  of,  64,  65 

fibrillated,  66 

growth  and  development  of,  79 

intercellular  substance  of,  64 

lymphoid  corpuscles  of,  67 

of  mesentery,  68 

plasma-cells  of,  67,  74 

reticular  form  of,  66 

of  liver,  188 

of  nerves,  126 

of  skin,  275 

Contraction,  study  of  muscular,  135 
Convoluted  renal  tubules,  205 
Corium,  277 
Cornea,  331 

preparation  of,  25 
Corneal  corpuscles,  75 

tissue,  75 

Corneous  layer  of  skin,  274 
Corniculum  of  larynx,  255 
Corona  radiata  of  brain,  317 

tubulorum,  316 
Corpora  cavernosa,  160 
Corpus  albicans,  250 

dentatum  cerebelli,  317 

luteum,  249 
Corpuscles,  colostrum,  450 


464 


INDEX. 


Corpuscles,  corneal,  75 

fixed,  of  cornea,  332 

lymphoid,  of  lymph-glands,  178 
of  skin,  277 

Malpighian,  of  spleen,  404 

of  bone,  90 

of  cartilage,  82,  83 

of  Donne,  450 

of  muscle,  136 

tactile,  124 

of  skin,  280 

of  tendon-tissue,  73 

yellow,  of  mamma,  444 
Corpus  striatum,  319 
Cortex  cerebri,  321 
Cortex  of  cerebellum,  319 

of  kidney,  201 

of  suprarenal  capsules,  432 
Corti's  membranes,  366 

organ,  362,  364 
Cowper's  glands,  227 
Creigh ton's  views  on  the  mamma,  445, 

446,  454 
Crista  acustica,  360 

spiralis,  364 
Crystalline  lens,  350 
Curara  for  producing  paralysis,  45 
Cuticula  of  teeth,  107 
Cylindrical  epithelium,  60 
Cystic  duct,  198 
Czermak,  interglobular  spaces  of,  103 

DARTOS,  231 
Daughter-cells  of  cartilage,  84 
Decidua,  245 

Deiter's,  protoplasmic  processes  of,  120 
Dentine,  103,  106 
Dentinal  canals,  104 

globules,  104 

teeth,  106 

Descemet's  membrane,  79,  333 
Detrusor  urinae,  430 
Development  of  blood-corpuscles,  47 

of  capillaries,  150 

of  bone,  96 

of  enamel,  108 

of  fat-tissue,  168 

of  hair,  293 

of  lymphatics.  175 

of  mamma,  452 

of  nail,  295 


Development  of  ovary,  250 

of  pancreas,  412 

of  sebaceous  glands,  286 

of  spleen,  409 

of  suprarenals,  436 

of  sweat-glands,  282 

of  teeth,  105 

of  thymus,  414 
Diaphragms,  5 
Dilator  muscle  of  iris,  342 
Direct  light,  5 

Division  of  cartilage  corpuscle,  84,  186 
Double  staining  with  borax  carmine  and 
indigo  carmine,  22 

with  cosine  and  aniline  colors,  24 
Doyere's  eminence,  126 
Drusenfeld  of  mamma,  452 
Duct,  cystic,  198 

of  pancreas,  411 

thoracic,  174 
Ducts,  ejaculatory,  235 

galactophorous,  441 
Ductus  communis,  198 
Dura  mater,  spinal,  296 


E 


AR,  353 

Eustachian  tube,  C55 

EXTERNAL  ear,  353 
auricle  of,  353 
meatus  of,  353 
membrana  tympani  of,  354 

INTERNAL  ear,  357 

"auditory  teeth"  of,  364 

cochlea  of,  362 

Corfci's   membrana    tectoria    of, 

366 

crista  acustica  of,  360 
crista  spiralis  of,  364 
Henson's  prop-cells  of,  366 
labium  tympanicum  of,  364 
labium  vestibulare  of,  364 
lamina  reticularis  of,  366 
lamina  spiralis  of,  362 
macula  acustica  of,  360 
membrana  basilaris  of,  364 
membrane  of  Reissner,  3G2 
membranous  labyrinth  of,  358 
modiolus  of,  362 
organ  of  Corti,  362,  364 
otoliths  of,  358 
recessus  internus  of,  364 


INDEX. 


405 


EAR- 
INTERNAL  ear— 
saccule  of,  358 
scala  tympani  of,  362 
scala  vestibuli  of,  362 
semicircular  canals  of,  359 
utricle  of,  358 
zona  pectinata  of,  366 

MIDDLE  ear,  355 
glands  of,  355 
structure  of,  355 
Ectasia  of  milk- ducts,  452 
Efferent  vessels  of  kidney,  206 
Ejaculatory  ducts,  235 
Elastic  fibres  of  skin,  277 
Elastic  tissue,  77 

fibres  of,  77 

networks  of,  78 

of  ligamentum  nuchse,  79 

perforated  membrane  of,  79 
Electricity,  action  of,  on  blood,  44 
Embedding  specimens,  15,  16 
Enamel,  102 
Enamel  organ,  primary,  107 

secondary,  107 
Endoneurium,  126 
Endothelium,  80 

and  stomata  of  lymphatics,  169 

germinating,  1G5 

vascular,  143 
Eosine,  24,  25 

and  haematoxylon,  25 
Ependyma,  320 
Epidermis,  271 
Epididymis,  231 
Epiglottis,  255 
Epineurium,  126 
Epithelium,  56 

bacteria  of,  57 

ciliated,  58 

columnar  or  cylindrical,  60 

granules  of,  61 

networks  of,  61 

pigmented,  58 

squamous  or  flattened,  57 

structure  of,  61 
Epithelium  of  bladder,  430 

of  collecting  tubules  of  kidney,  211 

of  involuted  mamma,  446 

of  looped  renal  tubules,  210 

of  lung,  261 
30 


Epithelium  of  mamma,  444 
of  mouth,  377 
olfactory,  371 
of  renal  tubules,  206 
of  spinal  cord,  301 
of  thyroid,  415 
Erector  pili  muscles,  422 
Etat  mamelojine  of  stomach,  389 
Eustachian  tube,  355 
Expanded  mamma,  structure  of,  444 
External  ear,  353 

External  elastic  coat  of  arteries,  155 
EYE,  328 

arteria  hyaloidea  of,  349 
caruncula  lachrymalis,  330 
CILIARY  body  of,  340 

in  hypermetropic  eye,  342 
in  myopic  eye,  341 
CHOROID,  338 

blood-vessels  of,  339 
lamina  chorio-capillaris  of,  339 
lamina  suprachoroidea  of,  338 
nerves  of,  340 
structure  of,  338 
CONJUNCTIVA,  330 

lymph- spaces  of,  331 
CORNEA,  331 

blood-vessels  of,  333 
Bowman's  membrane  of,  331 
Descemet's  membrane  of,  333 
fibrae  arcuatse  of,  332 
fixed  corpuscles  of,  332 
lamellse  of,  331 
nerves  of,  333 
preparation  of,  334 
EYELIDS,  328 

conjunctiva  fornicis,  329 
conjunctiva  tarsi,  328 
cilia  of,  328 

Meibomian  glands  of,  329 
muscle  of  Miiller,  329 
orbicularis  palpebrarum,  328 
Eiolani's  muscle  of,  329 
tarsus  of,  328 
Fontana's  space  of,  336 
IRIS,  342 

blood-vessels  of,  343 
dilator  muscle  of,  342 
ligament  of,  336 
nerves  of,  343 
sphincter  of,  342 


466 


INDEX. 


EYE- 
IRIS,  uvea  of,  343 

LACHRYMAL  gland,  351 

glandula  Galeni  of,  351 
glandula  Monroi  of,  351 

LENS,  350 

canal  of  Petit,  350 
ligament  of,  350 
ligamentumpectinatum  iridis,  335 

OPTIC  nerve,  348 

blood-vessels  of,  349 
circle  of  Haller,  349 
neuroglia  of,  348 
subdural  space  of,  348 
vagina  fibrosa  of,  348 

Orbicularis  ciliaris,  340 

Ora  serrata,  340 

RETINA,  343 

arteria  centralis  of,  347 
blood-vessels  of,  347 
ganglion-cell  layer  of,  344 
inner  granular  layer  of,  344 
inner  nuclear  layer  of,  345 
layer  of  rods  and  cones  of,  345 
macula  lutea  of,  344,  346 
membrana   limitans  externa  of, 

345 
membrana  limitans  interna  of, 

346 

outer  granular  layer  of,  345 
outer  layer  of,  nuclei  of,  345 
pars  ciliaris  of,  347 
pigment  layer  of,  346 
preparation  of,  347 

Schlenim's  canal,  336 

SOLERA,  337 

lamina  cribrosa  of,  337 
perichoroidal  space  of,  337 
structure  of,  337 
Tenon's  capsule  of,  337 
tunica  vasculosa  of,  338 
venae  vorticosae  of,  337 
vitreous  body,  349 
fossa  patellaris  of,  350 


TjULLOPIAN  TUBES,  246 
•*-      Fat-canals  of  cutis  vera,  421 
Fat-cells  of  skin,  276 
Fat-columns  of  cutis  vera,  421 
Fat-tissue,  73 


Fibrae  arcuatss  of  cornea,  332 
Fibres,  muscular,  128 
Fibrillation  of  cartilage,  83 
Fibrous  cartilage,  86 

tissue,  66 

Filum  terminale  of  spinal  cord,  302 
Finibriss  of  tongue,  380 
Fissure  of  Rolando,  321 

of  Sylvius,  321 
Fluid,  spinal,  297 
Follicles  of  Lieberkiihn,  398 

of  lymph-glands,  176 

of  thymus,  412 
Fontana's  spaces,  336 
Foramen  caecum  of  tongue,  383 
Formation  of  bone,  97 

of  callus,  100 
Formatio  reticularis  of  medulla  oblongata, 

308 

Fossae  nasales,  368 
Freezing  section-cutter,  17 
French  archil,  28 
Frog's  bladder,  muscle  of,  129 
Frommann's  lines,  113 


ALACTOBLASTS,  451 

Galactophorous  ducts,  441 
GaU-bladder,  197 
Ganglia,  cerebral,  319 
Ganglia  of  spinal  cord,  120 
Ganglionic  bodies,  119,  121 

corpuscles  of  brain,  72 
Gas-chamber,  43 
Gelatinous  tissue,  63 
Genital  organs,  female,  240 

male,  223 
Germinating  eudothelium,  165 
Giant-cells,  95 
Gibbes'   double,    triple,    and    quadruple 

staining,  26 
Griraldes,  organ  of,  231 
Grland,  coccygeal,  158 

inter-carotid,  160 

lachrymal,  351 

pineal,  417 

thymus,  412 

thyroid,  415 
Grlands,  Bowman's,  of  nose,  372 

lymphatic,  176 

Meibomian,  329 


INDEX. 


467 


Glands  of  Bartholine,  241 

of  bile-ducts,  101 

of  bronchi,  258 

of  Brunner,  397 

of  Cowper,  227 

of  larynx,  256 

of  middle  ear,  355 

of  small  intestine,  366 

of  tongue,  383 

peptic,  389 

pyloric,  391 

sebaceous,  of  skin,  285 

sudoriparous,  282 
Glans  clitoridis,  241 

penis,  224 

Glandules  aberrantes  mammas,  442 
Glandula  Galeni,  351 

Monroi,  351 

Glandules  of  mouth,  378 
Glisson's  capsule,  183 
Glosso-pharyngeal  root,  313 
Goblet  cells,  60 
Gold,  chloride  of,  28 
Goll,  column  of,  298 
Graafian  follicles,  248 
Granular  layer  of  skin,  274 
Gray  matter  of  spinal  cord,  299 
Green  coloration  of  nuclei,  25 
Growth,  post-embryonal,  of  mamma,  453 


TT^EMACHROMOMETER,  53 
H    Haemoglobin,  .53 
Haematoblasts,  47 
Haematometers,  50,  53 
Hsematoxylon,  preparation  of  nerves  in, 
118 

solution,  23,  24 
Hailes's  microtome,  19,  20 
Hair,  288 
Haller,  circle  of,  349 

circulus  venosus  of,  442 
Hamilton's  preservative  fluid,  20 
Hand  section-cutter,  16 
Hardening  of  brain,  15 
Haversian  canals  of  bone,  91 
Heart,  muscular  fibres  of,  140 
Heidenhain,  rods  of,  207 
Henson's  prop-cells,  366 
Hepatic  artery,  186 

cells,  189 


Hints  regarding  study  of  mamma,  455 

Horny  teeth,  106 

Howship's  lacunae,  100 

Hyaline  cartilage,  82 

Hydatid  of  Morgagni,  231 

Hymen,  241 

Hypermetropia,  ciliary  body  in,  342 

Hypoglossal  nucleus,  311 

TLLUMINATION,  4 

•*•    Induline,  27 

Infundibula  of  lung,  260 

Injecting  fluids,  30,  32 

Injection  of  blood-vessels,  30,  31,  32 

of  cutis  vera,  424 

of  kidney,  214 

of  liver,  185 

of  lymph-glands.  179 

of  lymphatics,  169 
Instrument,  care  of,  7 
Intercarotid  gland,  160 
Intercalated  portions  of  renal  tubules,  211 
Intercellular  substance  of  cartilage,  83 

of  connective  tissue,  64 
Intermuscular  tissue,  74 
Internal  capsule  of  brain,  317 
Internal  elastic  coat  of  arteries,  152 

of  veins,  157 
Internal  ear,  357 
Internal  fibrous  coat  of  arteries,  153 

of  veins,  157 
Intima  of  arteries,  152 
Invertebrates,  muscle  of,  133 
Involuntary  muscle-fibre,  128 
Involuted  mamma,  histology  of,  446 
Iodized  serum,  38 
Irrigation,  method  of,  41,  67 
Iris,  342 

diaphragm,  5 
Island  of  Reil,  322 
Ivory,  103 

YARYOKINESIS,  237 

-    Keyes's  method  of  counting  blood- 
globules,  51 
KIDNEY,  201 

afferent  vessel  of,  capsule  of,  206 
blood-vessels  of,  213 
Bowman's  capsules  of,  204 
calyx  of,  216 


468 


INDEX. 


KIDNEY— 

capsule  of,  216 
collecting  tubules  of,  205 
convoluted  tubes  of,  205 
efferent  vessel  of  capsules  of,  206 
epithelium  of  collecting  tubules,  211 
of  looped  tubules  of,  210 
of  tubules  of,  206 
general  plan  of  structure  of,  201 
boundary  layer,  201 
cortex,  201 
medulla,  201 
medullary  rays,  201 
injection  of,  214 
intercalated  portions  of  tubules  of, 

211 

looped  tubules  of,  209 
lymphatics  of,  216 
membrana  propria  of  tubules  of,  203 
method  of  preparing  sections  of,  208 
natural  injection  of  tubules  of,  216, 

220 

nerves  of,  216 
rods  of  Heidenhain,  207 
stroma  of,  215 
tubules  of,  203 
vasa  recta  of,  214 
Kleinenburg's  hasmatoxylon,  23 
Klein's  hsematoxylon,  24 
Klein's  method  of  studying  the  omentuni, 

166 
Kuhnt,  hohlcylinder  of,  114 


LABIA  MAJORA,  240 
minora,  240 
Labium  tympanicum,  364 

vestibulare,  364 
Labyrinth,  358 
Lachrymal  gland,  351 
Lacunae,  Howship's,  100 
Lacunas  of  bone,  91 
Lamellse  of  bone,  90 
Lamina  chorio-capillaris,  339 

cribrosa  of  solera,  337 

reticularis  of  ear,  366 

spiral  is,  362 

suprachoroidea,  338 
Large  intestine,  400 
Larynx,  253 
Lens,  350 


Lenses,  high,  testing  of,  10 

kinds  of,  6 

measuring  angle  of,  10 

testing  of,  8 
Leucocytes,  39,  48 
Lieberkiihn's  follicles,  398 
Ligament  of  iris,  336 

of  lens,  350 

Ligaments  of  larynx,  253 
Ligamentum  pectinatum  iridis,  335 
Light,  direct,  5 

oblique,  5 

Liquor  sanguinis,  34 
LIVER,  183 

acini  of,  183 

bile-ducts,  capillary,  192 

Mayer's  views  on,  196,  197 
natural  injection  of,  193 
walls  of,  196 

bile -ducts,  larger,  191 

blood-vessels  of,  186 

capsule  of,  183 

cells  of,  189 

central  veins  of,  184 

connective  tissue  of,  188 

cystic  duct,  198 

ductus  communis,  198 

fat-droplets  in  cells  of,  190 

gall-bladder,  197 
coats  of,  198 

glands  of  bile-ducts,  191 

Glisson's  capsule  of,  183 

general  plan  of  structure  of,  183 

hepatic  artery,  186 

hepatic  lobules,  183 

injection  of,  185 

inter lobular  septa  of,  188 

interlobular  veins  of,  184 

intermediate  canals  of,  184 

intralobular  veins  of,  184 

lymph-vessels  of,  198 

nerves  of,  199 

sublobular  veins  of,  185 
Lobule,  paracentral,  323 
Lobules  of  liver,  183 
Lobulettes  of  lung,  260 
Locus  cseruleus,  315 

niger,  316 

Looped  renal  tubules,  207 
Lumbar  enlargement  of  spinal  cord,  303 
Lungs,  257 


INDEX. 


469 


Lunula  of  nails,  294 
Luschka's  gland,  158 
Lymphangeal  nodules,  167 

tracts,  167 

Lymphatic  glands,  176 
Lymphatics  of  bladder,  431 
of  blood-vessels,  161 
of  kidney,  216 
of  large  intestine,  401 
of  larynx,  257 
of  liver,  198 
of  lung,  264 
of  mamma,  443 
of  mouth,  379 
of  oesophagus,  388 
of  pancreas,  411 
of  small  intestine,  399 
of  spleen,  409 
of  stomach,  393 
of  suprarenals,  436 
of  testis,  234 
of  thymus,  414 
of  thyroid,  416 
LYMPHATIC   SYSTEM,  163 

artificial  injection  of  lymphatics,  169 
cysternse  lymphaticse,  170 
development  of  fat-tissue,  168 
endolymphangeal  tracts,  167 
endothelium  and  stomata,  169 
general  histology  of,  164 
germinating  endothelium  of,  165 
glands  of,  175 

adenoid   or    reticular   tissue   of, 

178 
afferent  and  efferent  branches  of, 

176 

follicles  of,  176 
injection  of,  179 

lymphoid  corpuscles  of,  178 
medulla  and  cortex  of,  176 
methods  of  studying,  179 
nerves  of,  179 

Ranvier's  plan  of  injection  of,  180 
sinuses  of,  177 
stroma  of,  176 
vessels  of,  179 
Klein's  method  of  studying  omentum, 

1G6 
lymphangeal  nodules  or  patches   of, 

167 
lymphangeal  tracts  of,  167 


LYMPHATIC  SYSTEM— 

lymphatic  radicles,  course  and  ter- 
mination of,  168 
lymphatics,  175 

development  of,  175 
of  mesentery,  165 
of  tendons,  175 
lymphatic  vessels,  172 

intimate  structure  of,  172 
topographical  peculiarities  of,  174 
variations  in  shape  of,  173 
lymph-spaces,  175 

subarachnoid  and  subdural,  175 
modern  views  on,  163 
nerves  of  peritoneum,  172 
perilymphangeal  tracts,  167 
plasma-cells,  164 
plasmatic  channels,  165 
pseudo-stomata,  171 
Ranvier's  t aches  laiteuses,  168 

views  on  false  stomata,  170 
relations  to  connective  tissues,  163 
retrospective  view  of,  181 
sap-canaliculi  of,  165 
stomata  of,  165 
stomata  vera  of,  171 
thoracic  duct,  174 
Lymphoid  cells  of  brain,  72 
Lymphoid  corpuscles  of  connective  tissue, 
67 

of  lymph-glands,  178 
of  skin,  277 

Lymph-spaces,  subarachnoid,  175 
Lymph-vessels  of  penis,  224 


MACULA  ACUSTICA,  360 
lutea,  344,  346 

Malassez's  method  of  counting  blood-cor- 
puscles, 50 
Malpighian  corpuscles  of  spleen,  404 

layer  of  skin,  271 
Mammary  epithelium,  444 
MAMMARY  GLAND,  439 
areola  of,  442 
blood-vessels  of,  442 
circulus  venosus  of  Haller  of,  442 
colostrum    bodies,    or   corpuscles   of 

Donne,  450 
development  of,  452 
Driisenfeld,  452 


470 


INDEX. 


MAMMARY  GLAND— 

ectasia  of  miik-ducts,  452 
galactoblasts  of,  451 
galactophorous  ducts  of,  441 
general  considerations  on,  439 
glandulas  aberrantes  of,  442 
growth  of,  453 

Creighton's  views  on,  454 
Harderian  g-land,  similarity  with,  449 
lymphatics  of,  443 
membrana  propria  of,  449 
milk-globules,  451 
milk-reservoirs  of,  441 
nerves  of,  443 
nipple  or  mamilla  of,  440 
Partsch's  views  on  milk-secretion,  451 
Rauber's  views  on  the  mamma  and 

the  lacteal  secretion,  450 
structure  of  fully  expanded  gland,  444 
acini  of,  444 

Creighton's  views  on,  445 
epithelium  of,  444 
plasma-cells  of,  444 
yellow  cells  of,  444 
structure  of  involuted  mamma,  446 
Creighton's  account  of,  446 
epithelium  of,  446 
vacuolation  of  epithelium  of,  447 
study  of,  455 
St&iezeUen  of,  449 
Wendt's  views  on  secretion  of  milk, 

449,  451 
Mammilla,  440 
Marrow  of  bone,  95 

Measurement  of  red  blood-corpuscles,  35 
Meatus  auditorius  externus,  353 
urinarius  of  female,  242 

of  male,  226 

Media  or  musculosa  of  arteries,  154 
Medulla  of  suprarenal  capsules,  435 
oblongata,  307 
of  kidney,  201 

Medullary  rays  of  kidney,  201 
Meibomian  glands,  329 
Meissner's  plexus,  122,  399 
Mernbrana  basilaris  of  ear,  364 
limitans  olfactoria,  372 
propria  of  mamma,  449 
propria  of  renal  tubules,  203 
tectoria  of  ear,  366 
tympani,  354 


Membrane  of  Bowman,  79 
of  Corti,  366 
of  Descemet,  79 
of  Reissner,  3G2 
Meninges  of  brain,  321 
of  spinal  cord,  296 
Metallic  solutions,  28,  29 
Metaplastic  bone,  98 
Methods  for  preparing  objects,  12 
of  preparing  tissues,  14 
of  studying  hyaline  cartilage,  84 
of  studying  spinal  cord,  305 
Methyl -green,  29 

and  induline,  27 
Micrometer,  stage,  7 
Microscope,  how  to  use,  4 

testing  of,  7 
Microtome,  Hailes',  19,  20 

Vincent's,  21 
Middle  ear,  355 
Milk-ducts,  444 
Milk-globules,  451 
Milk- reservoirs,  441 
i  Miller's  picro-carmine,  23 
i  Mirrors,  5 
|  Modiolus,  362 
Moist  chamber,  42,  43 
Molybdate  of  ammonia,  15 
Morgagni,  hydatid  of,  231 
Motor  tract  of  hemispheres,  322 
MOUTH  AND   TONGUE,  377 
MOUTH,  377 

blood-vessels  of,  379 
epithelium  of,  377 
glandules  of,  378 
lymphatics  of,  379 
nerves  of,  379 
submucous  tissue  of,  377 
tunica  propria  of,  377 
TONGUE,  380 

circumvallate  papillae  of,  383 
glands  of,  383 

filiform  papillas  of,  380 
fimbrige  of,  380 
foramen  coecum  of,  383 
fungiform  papillae  of,  381 
papillse  foliatae  of,  383 
taste-goblets  of,  381 
Mucous  membrane  of  larynx,  255 
of  oesophagus,  386 
of  small  intestine,  395 


INDEX. 


471 


Mucous  membrane  of  stomach,  389 
Mucous  tissue,  63 
Muscle,  128 

Cohnheim's  areas  of,  136 

columns  of,  138 

conclusions  regarding  structure  of,  137 

fibres  of,  128 

of  frog's  bladder,  129 

of  fly,  133 

of  heart,  140 

of  human  embryo,  132 

of  invertebrates,  133 

of  the  ' '  lucky  bug  "  or  gyrinus, 

134 
of  water-beetles,  133 

involuntary,  128 

nuclei  and  corpuscles  of,  136 

peculiarities  of,  associated  with  differ- 
ent functions,  138 

polarized  light  for  the  study  of,  137 

red  and  white,  of  rabbit's  leg,  138 

sarcolemma,  130 

striation  of  fresh,  fibre,  131 

study  of  contraction  of,  135 

termination  of,  in  tendon,  139 

transverse  sections  of,  136 

vascular  supply  of,  138 

voluntary  fibre,  130 

of  Mailer,  329 

of  Riolani,  329 

termination  of  nerves  in,  125 
Muscles  of  skin.  287 
Muscular  coat  of  oesophagus,  387 

of  small  intestine,  394 

of  stomach,  388 

fibres  of  heart,  140 
Muscularis  mucosse  of  oesophagus,  387 

of  small  intestine,  396 

of  stomach,  389 
Musculosa  of  arteries,  154 
Mailer's  fluid,  14 

muscle,  329 
Myelinic  fibres  of  spinal  cord,  301 

nerve-fibres,  109,  116 
Myeloplaxes,  95 
Myopia,  ciliary  body  in,  341 

NABOTH,  ovula  of,  244 
Nail-fold,  294 
Nails,  293 
Naphthaline  yellow,  27 


NASAL  FOSSAE,  PHARYNX,  and  TON- 
SILS, 368 

NASAL  FOSSAE,  368 

Bowman's  glands  of,  372 
indifferent  cells  of,  371 
membrana  limitans,  olfactoria  of, 

372 

mucous  membrane  of,  368 
olfactory  cells  of,  371 
olfactory  epithelium  of,  371 
olfactory  nerves  of,  372 
olfactory  region  of,  370 
thicker  membrane  of,  369 
thinner  membrane  of,  369 
respiratory  region  of,  368 
vestibulum  nasi,  368 

PHARYNX,  373 

mucous  membrane  of,  373 
pharyngeal  tonsil  of,  373 

TONSILS,  373 
i  Natural  injection  of  liver,  193 

of  kidney,  216,  220 
Nerve-elements  of  spinal  cord,  299 
Nerve-fibres,  varieties  of,  109 
Nerves  of  bladder,  431 

of  blood-vessels,  161 

of  choroid,  340 

of  cornea,  333 

of  iris,  343 

of  kidney,  216 

of  large  intestine,  401 

of  larynx,  257 

of  liver,  199 

of  lung,  265 

of  lymph-glands,  179 

of  mamma,  443 

of  mouth,  379 

of  ossophagus,  388 

of  ovary,  248 

of  pancreas,  411 

of  penis,  225 

of  peritoneum,  172 

of  skin,  279 

of  small  intestine,  399 

of  spleen,  409 

of  stomach,  393 

of  suprarenals,  436 

of  thyroid,  416 

of  uterus,  245 

olfactory,  372 
Nerve -terminations,  109 


472 


INDEX. 


NERVOUS   SYSTEM,  109 

Auerbach's  plexus,  123 

axis-cylinder,  110 

connective  tissue  of  nerves,  126 

Deiter's  protoplasmic  processes,  120 

Doyere's  eminence,  126 

endoneurium,  125 

epineurium,  126 

fibres  of  Remak,  117,  118 

preparation  of,  in  hsematoxylon, 
118 

Frommann's  lines,  113 

ganglia  of  cranial  and  spinal  nerves, 
120 

ganglia  of  spinal   cord,   examination 
of,  120 

gang]  ionic  bodies,  119 
of  human  brain,  121 
of  sympathetic  system,  121 

Gasserian  ganglion,  examination   of, 
in  frog,  120 

general  histology  of,  109 

hoJdcyliuder  of  Kuhnt,  114 

incisions  of  Schmidt,  111 

Meissner's  plexus,  122 

methods  of  nerve-termination,  109 

motorial  plate,  126 

myelinic  fibres,  109 

nerves,  modern  conceptions  of, 
116 

myeline  or  medulla,  110 

Pacinian  bodies,  124 

perineurium,  127 

preparation   by   bichromate   of    am- 
monia, 115 

preparation  in  osmic  acid  and  picro- 
carmine,  118 

Ranvier's  nodes,  110 

sheath  of  Schwann,  110 

spiral  fibre  of  Beale,  122 

staining  of,  in  osmic  acid,  113 

staining  of,  in  picro-carmine,  111 

staining    of,     with    silver     nitrate, 
112 

tactile  corpuscles,  124 

termination  of  nerves,  123 
in  muscle,  125 
in  epithelial  bodies,  126 

varieties  of  nerve-fibres,  109 
Nervous  system,  central,  296 
Network  of  epithelial  cells,  61 


Neumann,  dentinal  sheath  of,  104 
Neuroglia,  70,  71 

fibrillse  of,  72 

of  optic  nerve,  348 

of  spinal  cord,  298 
Nipple,  440 
Nitrate  of  silver,  29 

staining  of  nerves  with,  112 
Norris  and  Shakespeare's  method  of  dou- 
ble staining,  22 
Nose,  368 
Nose-piece,  5 
Nuclei,  green  coloration  of,  25 

of  muscle,  136 
Nucleus  and  root  of  abducens,  314 

lenticularis  of  brain,  316 

of  hypoglossus,  311 

parolivary,  311 


OBJECT,  arrangement  of,  6 
size  of.  8 
Oblique  light,  5 
Odontoblasts,  104 
Odontomata,  105 
CEsophagus,  386 
Olfactory  epithelium,  371 
nerves,  372 
region,  370 
Olivary  body,  310 
Optic  nerve,  348 
thalami,  319 
Ora  serrata,  340 
Orbicularis  ciliaris.  340 
palpebrarum,  328 
Organ  of  Corti,  362,  364 

of  Giraldes,  231 
ORGANS   OF  GENERATION,  FEMALE, 
240 
CLITORIS,  240 

corpora  cavernosa  of,  241 
genital  nerve  corpuscles  of,  240 
glans  of.  241 

GLANDS  OF  BARTHOLINB,  241 
HYMEN,  241 

FALLOPIAN  TUBES,  246 
ampulla  of,  246 
fimbriffi  of,  246 
isthmus  of,  246 
LABIA  MAJORA,  240 
LABIA  MINORA,  240 


INDEX. 


473 


ORGANS  OF  GENERATION,  FEMALE— 
OVARY,  246 

blood-vessels  of,  247 

corpus  albicans  of,  250 

corpus  luteum  of,  249 

development  of,  250 

Graafian  follicles  of,  248 

nerves  of,  248 

stroma  of,  246 

tubes  of,  246 
PAROVARIUM,  250 
PLACENTA,  251 
URETHRA,  242 

meatus  urinarius  of,  242 
UTERUS — 

changes  of,  during  menstruation 
and  gestation,  245 

decidua,  245 

glands  of,  244 

mucous  membrane  of,  248 

plicae  palmatae  of,  243 

nerves  of,  245 

os  uteri,  244 

ovula  Nabothi,  244 

vessels  of,  245 
VAGINA,  241 

vascular  system  of,  242 
VESTIBULE,  241 

bulbi  vestibuli,  241 

ORGANS  OF  GENERATION,  MALE,  223 
COWPER'S  GLANDS,  227 
EPIDIDYMIS,  231 

blood-vessels  of,  234 
EJACULATORY  DUCTS,  235 
HYDATID  OP  MORGAGNI,  231 
karyokiuesis,  237 
ORGAN  OF  GIRALDES,  231 
PENIS,  223 

blood-vessels  of,  224 

genital  nerve-corpuscles  of,  225 

glans  penis,  224 

lymph-vessels  of,  224 

nerves  of,  225 

tunica  albuginea  of,  223 

Tyson's  glands  of,  224 
PROSTATE  GLAND,  227 

acini  of,  228 

blood-vessels  of,  229 

epithelium  of,  228 

nerves  of,  229 

vesicula  prostatica  of,  229 


ORGANS  OF  GENERATION,  MALE— 
SCROTUM,  231 

dartos  of,  231 
semen  or  sperma,  235 
seminal  vesicles,  235 
spermatoblasts,  236 
SPERMATOZOA,  225 

structure  of,  236 

development  of,  236 
TESTICLES,  229 

blood-vessels  of,  234 

corpus  Highmori  of,  230 

lymphatics  of,  234 

mediastinum  of,  230 

nerves  of,  234 

rete  testis,  231 

seminiferous  tubules  of,  231,  2H3 

septula  of,  230 

tunica  adnata  of,  230 

tunica  albuginea  of,  230 

tunica  vaginalis  communis  of,  230 
URETHRA,  225 

colliculus  seminalis  of,  225 

lacunas  Morgagnii  of,  226 

lymphatics  of,  227 

meatus  urinarius  of,  226 

membranous  portion  of,  226 

musculus  urethralis  of,  226 

nerves  of,  226 

papillae  of,  226 

prostatic  portion  of,  225 

spongy  portion  of,  226 

structure  of,  225 
vas  aberrans,  232 
VAS  DEPERENS,  232,  233 

ampulla  of,  232 

muscular  coat  of,  234 

nerves  of,  234 
Organs  of  respiration,  253 
Osmic  acid,  staining  of  nerves  with,  113 
Osmic  acid  and  picro-carmine,  preparation 

of  nerves  in,  118 
Osmic  and  chromic  acids,  15 
Osmic  and  oxalic  acids,  staining  with,  28 
Ossification,  points  of,  98 
Osteoblasts,  96,  98 
Osteoclasts,  100 
Osteo-  or  vaso-dentine,  105 
Osteoporosis.  9 
Os  uteri,  244 
Otoliths,  358 


474 


INDEX. 


Ovary,  246 
Oviducts,  246 
Ovula  Nabothi,  244 


PACINIAN  BODIES,  134 

•*-     PANCREAS,  410 

acini  of,  420 

blood-vessels  of,  411 

centro-acinal  cells  of,  411 

development  of,  412 

excretory  duct  of,  411 

lymphatics  of,  411 

nerves  of,  411 

trypsin,  410 

zymogen,  410 
Panniculus  adiposus,  277 
Papillse  of  cutis  vera,  421 
of  hair,  289 
of  tongue,  380 
Papillary  sphincter,  429 
Paracentral  lobule,  323 
Parenchymatous  cartilage,  83 
Parolivary  nucleus,  311 
Parovarium,  250 

Partsch's  views  on  secretion  of  milk,  451 
Pavement  endothelium,  80 
Pelvis,  renal,  428 
Penis,  223 
Peptic  glands,  389 
Perichondrium,  86 
Perineurium,  126 
Periodontium,  108 
Periosteum,  95 
Perithelium,  148 
Peri  vascular  spaces,  161 
Petit,  canal  of,  350 
Peyer's  patches,  396 
Pharyngeal  tonsil,  373 
Pharynx,  873 
Pia  mater,  spinal,  297 
Picro-carmine.  23 

staining  of  nerve-fibres  with,  111 
Picro-haematoxylon  and  eosine,  26 
Pigmented  epithelium,  58 
Pigment  of  retina,  346 
Pineal  gland,  417 
Pituitary  body,  417 
Placenta,  251 
Plasma,  34 
cells,  164 


Plasma  of  connective  tissue,  67 

of  mamma,  444 
Plasmatic  channels,  165 
Pleura,  265 

Pleural  appendages,  267 
Plexus,  choroid,  320 

of  Auerbach,  399 

of  Meissner,  399 
Polarized  light  in  the  study  of  muscle, 

137 

Pons  varolii,  315 

Potassium  bichromate  solution,  14 
Preparation  of  bone,  92 

of  cornea,  334 

of  fresh  object,  13 

of  tissues,  13,  14 

of  mamma,  455 

of  microscopic  objects,  12 

of  retina,  347 

spleen,  409 

Preserving  fluid,  Wickersheimer's,  29 
Preservative  fluid,  Hamilton's,  20 
Prickle  cells,  58 

of  skin,  272 

Prop-cells,  Henson's,  366 
Prostate  gland,  227 
Pseudostomata,  171 

of  pulmonary  lymphatics,  264 
Pulp  of  spleen,  406 

of  teeth,  102,  105 

Purpurine  for  staining  cartilage,  85 
Purkinje,  cells  of,  318 

granular  layer  of,  104 
Purpurine,  28 
Pyloric  glands,  391 


T)  ADICLES  of  lymphatics,  168 
-t^    Ramification  of  capillaries,  149 
Ranvier's  nodes,  110 
purpurine,  28 
tacJies  laiteuses,  168 
Raphe  of  medulla  oblongata,  309 
\  Rauber's  views  on  the  mamma,  450 
j  Rectum,  401 
i  Red  blood-corpuscles,  34 
Reil,  island  of,  322 
Reissner,  membrane  of,  362 
Remak,  fibres  of,  117 
Renal  pelvis,  428 
tubules,  203 


INDEX. 


475 


RESPIRATORY  TRACT,  253 
LARYNX,  253 

calcification  of  cartilages  of,  255 

cartilages  of,  254 

cartilago  triticea  of,  253 

corniculum  of,  255 

epiglottis  of,  255 

glands  of,  256 

ligaments  and  membranes  of,  253 

lymphatics  of,  257 

mucous  membrane  of,  255 

nerves  of,  257 

Santorini's  cartilages  of,  255 

vocal  cords  of,  254 

Wrisberg's  cartilages  of,  255 
LUNGS,  259 

acini  or  lobulettes  of,  260 

alveolar  passages  of,  260 

alveoli  or  air-cells  of,  260 

blood-vessels  of,  263 

bronchioles  of,  260 

epithelium  of  alveoli  of,  261 

infundibula  of,  260 

lymphatics  of,  264 

nerves  of,  265 

pleural  appendages,  267 

pleura  of,  265 

pseudostomata  of  lymphatics  of, 
264 

septa  of,  262 

smaller  bronchi,  259 

subpleural  lymphatics,  237 

terminal  arteries  of,  263 
TRACHEA  and  PRIMARY  BRONCHI,  257 

cartilage  rings  of,  257 

glands  of,  258 

mucous  membrane  of,  257 
Rete  Malpighii,  271 

Reticular  or  yellow  elastic  cartilage,  85 
Reticular  form  of  connective-tissue,  66 
Retina,  342 

Retzius,  stripes  of,  103 
Riolani's  muscle,  329 
Rolando,  fissure  of,  321 
Root  of  hair,  283,  292 
of  nail,  294 

a  ACCITLE  of  labyrinth,  358 
^     Salter,  incremental  lines  of,  105 
Santorini's  cartilage,  255 
Sap-canaliculi,  165 


Sarcolemma,  130 
Sattertbwaite's  section-cutter,  17 
Scala  tympani,  362 

vestibuli,  362 
Scales  of  epidermis,  275 
Schlemm's  canal,  336 
Schmidt,  incisures  of,  111 
Schreger,  lines  of,  105 
Schwann,  sheath  of,  110 
Sclera,  337 
Scrotum,  231 
Sebaceous  glands,  285 
Section-cutters,  16,  17 
Semen,  235 

Semicircular  canals,  359 
Seminal  vesicles,  235 
Seminiferous  tubules,  231 
Septa  of  lung,  262 
Shaft  of  hair,  288,  292 
Sharpey's  fibres  of  bone,  94 
Sheath  of  Schwann,  110 
Sheaths  of  hair,  289 
Silver,  nitrate  of,  29 
Sinuses  of  lymph-glands,  177 
Size  of  object,  8 
SKIN,  269 

blood-vessels  of,  279 
CORIUM  OF,  277 

pars  papillaris,  278 
pars  reticularis  of,  278 
corneous  layer  of,  274 
elastic  tissue  fibres  of,  277 
epidermic  scales,  275 
EPIDERMIS,  271 

general  plan  of  arrangement  of, 

269 

general  structure  of,  270 
granular  layer  of,  274 
HAIR,  288 

development  of,  293 
papillae  of,  289 
root  of,  288,  292 
shaft  of,  288,  292 
sheaths  of,  289 
lymph  oid  corpuscles  of,  277 
muscles  of,  287 
NAILS,  293 
bed  of,  294 
body  of,  294 
development  of,  294 
lunula  of,  294 


476 


INDEX. 


SKIN- 
NAILS — 

nail  and  fold,  294 
root  of,  294: 

nerves  of,  279 

panniculus  adiposus  of,  276 

rete  Malpighii,  271 

prickle  cells  of,  272 

SEBACEOUS  GLANDS  OF,  285 
development  of,  286 

stratum  lucidum  of,  274 

stratum  subpapillare  of,  279 

subcutaneous  connective-tissue  layer 
of,  278 

fat-cells  of,  276 

SWEAT-GLANDS  OF,  283 
development  of,  285 

tactile  corpuscles  of,  280 
Slide  for  heating,  40 
Small  intestine,  394 
Sperma,  235 
Spermatoblasts,  236 
Spermatozoa,  235 
Sphincter  of  iris,  342 

ani,  401 

papillary,  429 

vesicge,  430 
Spinal  cord,  298 

fluid,  397 

Spina's  views  on  cartilage,  87 
SPLEEN,  403 

blood-vessels  of,  407 

development  of,  409 

fibrous  coat  or  capsule  of,  404 

general  structure  of,  403 

lymphatics  of,  409 

Malpighian  corpuscles  of,  404 

nerves  of,  409 

preparation  of,  409 

pnlp  of,  406 

serous  coat  of,  403 
Squamous  epithelium,  57 
Stage  diaphragms,  5 

micrometer,  7 

Stevenson,  plan  of  imbedding,  1C 
Stomach,  388 
Stomata  of  lymph-vessels,  165 

vera,  171 
Stratum  intermedium  of  tooth,  108 

lucidum  of  skin,  274 

subpapillare  of  skin,  279 


Striation  of  muscle,  331 
Stroma  of  kidney,  215 
Stutzzellen  of  mamma,  449 
Subdural  spaces  of  optic  nerve,  348 
Submucous  layer  of  oesophagus,  387 
of  small  intestine,  396 
of  stomach,  389 
Subpleural  lymphatics,  267 
Sudoriferous  glands,  282 
SUPRARENAL  CAPSULES,  431 
blood-vessels  of,  436 
capsule  of,  432 

cortical  substance  of,  432 
external  layer  of,  433 
internal  layer  of,  435 
middle  layer  of,  433 
zona  fasciculata  of,  433 
zona  glomerulosa  of,  433 
zona  reticularis  of,  436 
development  of,  436 
lymphatics  of,  436 
medullary  substance  of,  435 
nerves  of,  436 
Sweat-glands,  282 
Sylvian  fissure,  321 
Sympexions  of  thyroid,  415 


mACTILE  CORPUSCLES,  124 
•*•     Tarsus  of  eye,  328 
Taste-globlets  of  tongue,  381 
TEETH,  102 

cement  of,  105 
dentinal  canals  of,  104 
dentinal  globules  of,  104 
dentinal  fibres  of  tomes,  104 
dentinal  sheath  of  Neumann,  1 04 
dentine  or  ivory,  103 
development  of,  105 

cuticula,  107 

dentinal  teeth,  106 

dentine,  106 

horny  teeth,  106 

primary  enamel  organ,  107 

secondary  enamel  organ.  107 

stratum  intermedium  of,  108 

tooth  papilla,  107 

tooth-sac,  107 

development  of  enamel  of,  108 
enamel,  102 
granular  layer  of  Purkinje,  104 


INDEX. 


477 


TEETH— 

incremental  lines  of  Salter,  105 

interglobular  spaces  of  Czermak,  103 

interglobular  substance,  105 

lines  of  Schreger,  105 

parallel  stripes  of  Retzius,  103 

parts  of,  102 

periodontium  of,  108 

pulp  of,  102,  105 

odontoblasts,  104 

odontomata,  105 

osteo-  or  vaso-dentine,  105 
Tendons,  lymphatics  of,  175 
Tendon-tissue,  72 
Tenon's  capsule,  337 
Termination  of  muscle  in  tendon,  139 
Testicles,  229 
Testing  lenses,  8,  10 

microscope,  7 
Thalami  optici,  319 
THICK  CUTIS  VERA,  420 

blood-vessels  of,  423 

erector  pili  muscles  of.  422 

fat-columns  or  fat-canals  of,  421 

fibrous  prolongations  of,  420 

injection  of,  424 

lymphatics  of,  424 

papillse  of,  421 

Third  corpuscular  element  of  blood,  48 
Thoracic  duct,  174 
THYMUS  GLAND,  412 

blood-vessels  of,  414 

capsule  of,  412 

cells  of,  413 

central  canal  of,  414 

development  of,  414 

follicles  of,  412 

lymphatics  of,  414 

thymic  juice  of,  413 
THYROID  BODY,  415 

blood-vessels  of,  416 

capsule  of,  415 

epithelium  of,  415 

lymphatics  of,  416 

nerves  of,  416 

sympexions  of,  416 

vesicles  of,  415 
Tissue,  adenoid,  69 

cellular,  63 

connective,  63 

corneal,  75 


Tissue,  elastic,  77 

fat,  73 

fibrous,  66 

gelatinous,  63 

intermuscular,  74 

mucous,  63 

tendon,  72 

Tissue,  compact,  of  bone,  89 
Tomes,  dentinal  fibres  of,  104 
Tongue,  380 
Tooth-sac,  107 
Tonsil,  pharyngeal,  373 
Tonsils,  373 
Trachea,  257 
Triple  staining,  26 
Trypsin,  410 
Tubules  of  kidney,  203 
Tubules,  seminiferous,  231 
Tunica  vasculosa  of  solera,  338 
Tympanum,  354 
Types  of  arteries,  152 
Tyson's  glands,  224 


TTRETERS,  429 
<~>    Urethra,  female,  243 

male,  225 
URINARY    EXCRETORY    PASSAGES, 

428 
BLADDER,  430 

blood-vessels  of,  431 
epithelium  of,  430 
connective  tissue  of,  430 
detrusor  urinas  of,  430 
lymphatics  of,  431 
muscular  coat  of,  430 
nerves  of,  431 
sphincter  vesicae,  430 
RENAL  PELVIS,  428 
fibrous  layer  of,  429 
mucous  membrane  of,  428 
muscular  coat  of,  429 
papillary  sphincter  of,  429 
vessels  and  nerves  of,  429 
URETERS,  429 

mucous  membrane  of,  429 
muscular  layers  of,  429 
vessels  and  nerves  of,  429 

Uterus,  243 

Utricle  of  labyrinth,  358 

Urea,  343 


478 


INDEX. 


TTACUOLATION   of   mammary   epithe- 
V          liurn,  447 
Vagina,  241 
Valves  of  veins,  158 
Valvulae  conniventes,  395 
Vas  aberrans,  232 
Vasa  recta  of  kidney,  214 
Vas  deferens,  232 
Vasa  vasorum,  161 
Veins,  156 

central,  of  liver,  184 

interlobular,  of  liver,  1 84 

intralobular,  of  liver,  184 

sublobular,  of  liver,  185 
Venge  vorticosae  of  sclera,  337 
Ventricles  of  brain,  319 
Venules,  156 
Vermiform  appendix,  401 
Vertebrates,  muscle  of,  130 
Vesical  epithelium,  430 
Vesiculas  seminales,  235 
Vessels  of  muscle,  138 
Vestibule  of  vagina,  241 
Vestibulum  nasi,  368 
Villi  of  intestine,  395 
Vincent's  microtome,  21 


Violet  de  Paris,  29 
Vitreous  body,  349 
Vocal  cords,  254 
Voluntary  muscle  -fibre,  130 

TIT  ARM-SLIDE,  40 

Waxy  change,  methyl-gieen  for,  29 
Wendt,  method  of  triple  staining,  26 

views  on   endothelial  desquamaticn, 
147 

views  on  secretion  of  milk,  449,  451 
White  blood-globules,  39,  48 
White  substance  of  spinal  cord,  299 
Wickersheimer's  preserving  fluid,  29 
Wrisberg's  cartilage,  255 


W  CELLS  of  mamma,  444-. 


I70NA  FASCICULATA   of   suprarenals, 
^     433 

glomerulosa,  433 

reticularis,  433 

pectinata  of  ear,  366 
Zymogen,  410 


